Heat pump cycle

ABSTRACT

In a heat pump cycle, refrigerant tubes of an outdoor heat exchanger serving as an evaporator for evaporating refrigerant, and cooling fluid tubes of a radiator for dissipating heat from a coolant of an electric motor for traveling serving as an external heat source are bonded to the same outer fins. The heat contained in the coolant flowing through the cooling fluid tubes can be transferred to the refrigerant tubes of the outdoor heat exchanger via the outer fins. Thus, in the defrosting operation which involves defrosting the outdoor heat exchanger by flowing the coolant through the radiator, the loss in transfer of the heat contained in the coolant to the outdoor heat exchanger can be suppressed, and the heat supplied from the electric motor for traveling can be effectively used for defrosting the outdoor heat exchanger.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No.2010-132891 filed on Jun. 10, 2010, and No. 2011-123199 filed on Jun. 1,2011, the contents of which are incorporated herein by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates to a heat pump cycle for performing adefrosting operation to remove frost formed in a heat exchanger servingas an evaporator. More specifically, the invention relates to a heatpump cycle suitably used for an air conditioner for a vehicle that has adifficulty in obtaining a heat source for heating from a driving sourcefor traveling.

BACKGROUND OF THE INVENTION

Conventionally, Patent Document 1 discloses a vapor compressionrefrigeration cycle (heat pump cycle) that performs a defrostingoperation for melting and removing frost formed in a heat exchangerserving as an evaporator for evaporating refrigerant.

The heat pump cycle disclosed in Patent Document 1 is applied to an airconditioner for a hybrid car. The heat pump cycle is designed to becapable of switching between a heating operation for heating theinterior of a vehicle by heating air blown into a vehicle compartment asa heat exchange fluid, and a defrosting operation for removing frostformed in an outdoor heat exchanger serving as the evaporator in theheating operation.

More specifically, in the defrosting operation, when the frost formationof the outdoor heat exchanger is detected, an internal combustion engine(engine) for outputting a driving force for vehicle traveling isinitiated, and warm air blown from a radiator for dissipating heat froman engine coolant is blown into the outdoor heat exchanger to therebydefrost the outdoor heat exchanger.

In short, the heat pump cycle disclosed in Patent Document 1 is designedto remove the frost formed in the outdoor heat exchanger by melting thefrost using waste heat of the engine as an external heat source.

PRIOR ART DOCUMENT

-   Patent Document 1: Japanese Unexamined Patent Publication No.    2008-221997

However, the structure for transferring heat absorbed by the coolantfrom the engine to the evaporator via air might dissipate heat from theair (warm air) heated by the radiator into ambient air, thereby leadingto the loss in heat transfer, as in Patent Document 1. In some cases,the waste heat from the engine as the external heat source cannot beeffectively used for defrosting the evaporator.

As mentioned above, the waste heat from the engine cannot be effectivelyused for defrosting the evaporator, which takes a long time to performthe defrosting. And, during the defrosting operation, the engine has tocontinue working, causing the deterioration of the fuel efficiency ofthe vehicle. When the heating operation is stopped during the defrostingoperation, a passenger cannot feel warm enough.

SUMMARY OF THE INVENTION

The present invention has been made in view of the forgoing points, andit is a first object of the present invention to provide a heat pumpcycle that can effectively use the heat supplied from an external heatsource during a defrosting operation.

Further, it is a second object of embodiments of the invention toprovide a heat pump cycle applied to an air conditioner for a vehicle,which can achieve both the effective use of heat supplied from theexternal heat source, and the prevention of insufficient heating to apassenger during a defrosting operation.

To achieve the above object, according to a first exemplar of thepresent invention, a heat pump cycle includes: a compressor compressingand discharging refrigerant; a user-side heat exchanger exchanging heatbetween the refrigerant discharged from the compressor and a heatexchange fluid; a decompression device decompressing the refrigerantflowing from the user-side heat exchanger; and an outdoor heat exchangerwhich causes the refrigerant decompressed by the decompression device toexchange heat with outside air and to be evaporated. The heat pump cycleis adapted to perform a defrosting operation for defrosting the outdoorheat exchanger when the outdoor heat exchanger is frosted. The heat pumpcycle further includes a heat-dissipation heat exchanger and a coolingfluid circuit switching device. The heat-dissipation heat exchanger isdisposed in a cooling fluid circulation circuit for circulating acooling fluid for cooling an external heat source, and is adapted toexchange heat between the cooling fluid and outside air. The coolingfluid circuit switching device is configured to switch between a coolingfluid circuit for allowing the cooling fluid to flow into theheat-dissipation heat exchanger, and a cooling fluid circuit forallowing the cooling fluid to bypass the heat-dissipation heatexchanger. In the heat pump cycle, the outdoor heat exchanger includes arefrigerant tube in which the refrigerant decompressed by thedecompression device flows, a heat-absorption air passage for flowingthe outside air is formed around the refrigerant tube, theheat-dissipation heat exchanger includes a cooling fluid tube in whichthe cooling fluid flows, a heat-dissipation air passage for flowing theoutside air is formed around the cooling fluid tube, the heat-absorptionair passage and the heat-dissipation air passage are provided with anouter fin that enables heat transfer between the refrigerant tube andthe cooling fluid tube while promoting heat exchange in both of theoutdoor heat exchanger and the heat-dissipation heat exchanger, and thecooling fluid circuit switching device performs switching to the coolingfluid circuit for flowing the cooling fluid into the heat-dissipationheat exchanger in at least the defrosting operation.

Because the cooling fluid circuit switching device performs switching tothe cooling fluid circuit for flowing the cooling fluid into theheat-dissipation heat exchanger during the defrosting operation, theheat contained in the cooling fluid flowing through the cooling fluidtube can be transferred to the outdoor heat exchanger to defrost theoutdoor heat exchanger.

At this time, outer fins are provided in the heat-absorption air passageand another heat-dissipation air passage to enable heat transfer betweenone refrigerant tube and another cooling fluid tube. Via the outer fins,the heat of the cooling fluid can be transferred to the outdoor heatexchanger.

As compared to the related art structure in which heat contained in thecooling fluid is transferred to the outdoor heat exchanger via air, theloss in heat transfer can be suppressed, and thus the heat supplied fromthe external heat source can be effectively used to defrost the outdoorheat exchanger during the defrosting operation. Further, the reductionin time required for the defrosting operation can also be achieved.

According to a second exemplar of the present invention, the heat pumpcycle of the above first exemplar further includes: an indoor evaporatorfor allowing the refrigerant on a downstream side of the outdoor heatexchanger to exchange heat with the heat exchange fluid and to beevaporated; and a refrigerant flow path switching device configured toswitch a refrigerant flow path in the heating operation in which therefrigerant discharged from the compressor flows into the user-side heatexchanger to heat the heat exchange fluid, and a refrigerant flow pathin the cooling operation in which the refrigerant dissipating heattherefrom at the outdoor heat exchanger flows into the indoor evaporatorto cool the heat exchange fluid. Furthermore, a flow direction of therefrigerant flowing through the refrigerant tube in the heatingoperation is the same as that of the refrigerant flowing through therefrigerant tube in the cooling operation.

This arrangement of the heap pump cycle can heat the heat exchange fluidby the user-side heat exchanger. Additionally, the heat pump cycle alsoincludes an indoor heat exchanger, and thus can also cool the heatexchange fluid by use of the indoor heat exchanger.

During the heating operation, the flow direction of refrigerant flowingthrough the refrigerant tube is the same as that of refrigerant flowingthrough the refrigerant tube during the cooling operation. As viewedfrom the flow direction of the outside air, the positional relationshipbetween a heat exchange region on a refrigerant inlet side of theoutdoor heat exchanger and a heat exchange region on a refrigerantoutlet side thereof does not change between the heating operation andthe cooling operation.

Thus, the outdoor heat exchanger and the heat-dissipation heat exchangerare macroscopically regarded as one heat exchanger. In the coolingoperation for dissipating heat from the refrigerant by the outdoor heatexchanger, a heat exchange region on the refrigerant inlet side of theoutdoor heat exchanger for flowing the refrigerant having a superheatdegree at a relatively high temperature is superimposed in the flowdirection of the outside air, on a heat exchange region on the coolingfluid inlet side of the heat-dissipation heat exchanger for flowing thecooling fluid at a relatively high temperature. Further, a heat exchangeregion on the refrigerant outlet side of the outdoor heat exchanger forflowing the refrigerant having a superheat degree at a relatively lowtemperature is superimposed in the flow direction of the outside air, ona heat exchange region on the cooling fluid outlet side of theheat-dissipation heat exchanger for flowing the cooling fluid at arelatively low temperature. With this arrangement, the flow of therefrigerant and the flow of the cooling fluid flowing through both heatexchangers can be made parallel.

Further, with this arrangement, in the heating operation for evaporatingthe refrigerant by the outdoor heat exchanger, the heat exchange regionon the refrigerant inlet side of the outdoor heat exchanger throughwhich the refrigerant flows at a relatively low temperature can besuperimposed on the heat exchange region on the cooling fluid inlet sideof the heat-dissipation heat exchanger through which the cooling fluidflows at a relatively high temperature, in the flow direction of theoutside air. Thus, the heat pump cycle of this embodiment caneffectively suppress the frost formation caused in the heat exchangeregion on the refrigerant inlet side of the outdoor heat exchangerthrough which the refrigerant flows at a relatively low temperature.

According to a third exemplar of the present invention, the heat pumpcycle of the above first or second exemplar is configured such that, inthe defrosting operation, an inflow rate of the refrigerant flowing intothe outdoor heat exchanger is decreased as compared to before transferto the defrosting operation.

Thus, in the defrosting operation, heat transmitted to the outdoor heatexchanger via outer fins can be prevented from being absorbed in therefrigerant flowing through the refrigerant tube of the outdoor heatexchanger. As a result, the heat supplied from the external heat sourcecan be used more effectively to defrost the outdoor heat exchangerduring the defrosting operation.

Furthermore, as in a fourth exemplar of the present invention, thedecompression device may be a variable throttle mechanism in which athrottle opening degree is variable, and the decompression device mayincrease the throttle opening degree in the defrosting operation ascompared to before transfer to the defrosting operation. Thus, in thedefrosting operation, high-temperature refrigerant discharged from thecompressor can readily flow to the outdoor heat exchanger, therebyaccelerating defrosting of the outdoor heat exchanger.

Furthermore, as in a fifth exemplar of the present invention, the heatpump cycle may further include an outflow rate adjustment valveconfigured to adjust an outflow rate of the refrigerant flowing from theoutdoor heat exchanger, and the outflow rate adjustment valve maydecrease the outflow rate of the refrigerant in the defrosting operationas compared to before transfer to the defrosting operation.

Furthermore, as in a sixth exemplar of the present invention, theoutflow rate adjustment valve may be configured integrally with anoutlet for the refrigerant of the outdoor heat exchanger. Thus, arefrigerant passage volume from a discharge port side of the compressorto an inlet side of the outflow rate adjustment valve can be reduced,thereby reducing a refrigerant flow amount flowing into the outdoor heatexchanger.

According to a seventh exemplar of the present invention, the heat pumpcycle of any one of first to sixth exemplars further includes an outdoorblower which blows outside air toward both the outdoor heat exchangerand the heat-dissipation heat exchanger, and the outdoor blowerincreases an air blowing capacity when the compressor is stopped, ascompared to before stopping the compressor.

When the compressor is stopped, the blowing capacity of the outdoorblower can be increased to thereby quickly increase the temperature ofthe outdoor heat exchanger to the same level as the outside air, whichcan further reduce the defrosting time. The term “when a compressor isstopped” means that the compressor is stopped not only during thedefrosting operation, but also during the normal operation.

In an eighth exemplar of the present invention, the heat pump cycleaccording to any one of first to seventh exemplars is configured suchthat, in the defrosting operation, a heating capacity of the user-sideheat exchanger for heating the heat exchange fluid is decreased ascompared to before transfer to the defrosting operation.

Thus, the heating capacity of the user-side heat exchanger for the heatexchange fluid is decreased, so that the amount of heat absorbed fromthe refrigerant at the outdoor heat exchanger can be reduced to promotethe defrosting. Specific means for decreasing the heating capacity ofthe user-side heat exchanger for the heat exchange fluid may include thereduction of a flow rate of refrigerant circulating through the cycle,and the reduction of a refrigerant pressure at the user-side heatexchanger.

According to a ninth exemplar of the present invention, in the heat pumpcycle according to any one of the first to eighth exemplars, theheat-absorption air passage and the heat-dissipation air passage areconfigured such that volumes of the outside air flowing into theheat-absorption air passage and the heat-dissipation air passage aredecreased in the defrosting operation.

Thus, the heat pump cycle can suppress the absorption of the heattransmitted to the outdoor heat exchanger via the outer fins, in theoutside air flowing through the heat-absorption air passage and theheat-dissipation air passage during the defrosting operation, and thuscan more effectively use the heat supplied from the external heat sourceto defrost the outdoor heat exchanger in the defrosting operation.

Specifically, an outdoor blower may be provided for blowing the outsideair toward both the outdoor heat exchanger and the heat-dissipation heatexchanger. During the defrosting operation, the blowing capacity of theoutdoor blower may be reduced to thereby decrease the volume of outsideair flowing into the heat-absorption air passage and theheat-dissipation air passage.

Further, a shutter device (passage interruption means) may be providedfor opening and closing an inflow route for allowing the outside air toflow into the heat-absorption air passage and the heat-dissipation airpassage. During the defrosting operation, the shutter device maydecrease a passage area of the inlet route of the outside air to therebydecrease the volume of outside air flowing into the heat-absorption airpassage and the heat-dissipation air passage.

The term “decreasing the volume of outside air” means not onlydecreasing the volume of air as compared to the present volume of inflowair, but also setting the volume of air to zero (0) (that is, notallowing the outside air to flow thereinto).

In a tenth exemplar of the present invention, the heat pump cycleaccording to any one of first to ninth exemplars further includes anoutdoor blower which blows outside air toward both the outdoor heatexchanger and the heat-dissipation heat exchanger. In this case, theheat-dissipation heat exchanger is located on a windward side in theflow direction of the outside air blown by the outdoor blower withrespect to the outdoor heat exchanger.

Because the outside air whose heat is absorbed by the heat-dissipationheat exchanger flows into the outdoor heat exchanger, the heat of thecooling fluid can be transferred to the outdoor heat exchanger not onlyvia the outer fins but also via air. Thus, during at least thedefrosting operation, the heat supplied from the external heat sourcecan be used more effectively to defrost the outdoor heat exchanger.

In an 11th exemplar of the present invention, in the heat pump cycleaccording to any one of first to tenth exemplars, at least one of therefrigerant tubes is located between the cooling fluid tubes, at leastone of the cooling fluid tubes is located between the refrigerant tubes,and at least one of the heat-absorption air passage and theheat-dissipation air passage is formed as one air passage.

Thus, as compared to the case where the heat-dissipation heat exchangerand the outdoor heat exchanger are arranged in series with respect tothe flow direction of the outside air, the cooling fluid tube and therefrigerant tube can be arranged close to each other. In other words,the cooling fluid tube can be positioned near frost formed in therefrigerant tube. Thus, during the defrosting operation, the heatsupplied from the external heat source can be effectively transmitted tothe outdoor heat exchanger to perform the defrosting operation.

According to a 12th exemplar of the present invention, the heat pumpcycle of any one of first to 11th exemplars may be applied to an airconditioner for a vehicle, and may include an inside air temperaturedetection portion configured to detect an inside air temperature of avehicle interior, and a frost formation determination portion configuredto determine frost formation of the outdoor heat exchanger. In thiscase, the heat exchange fluid is air blown into the vehicle interior,the external heat source is a vehicle-mounted device generating heat inoperation, the cooling fluid is a coolant for cooling thevehicle-mounted device, and the cooling fluid circuit switching deviceperforms switching to the cooling fluid circuit for flowing the coolingfluid into the heat-dissipation heat exchanger when the frost isdetermined to be formed at the outdoor heat exchanger by the frostformation determination portion and an inside air temperature of thevehicle interior is equal to or more than a predetermined referenceinside air temperature.

With this arrangement, the frost formation is determined by a frostformation determination portion, and when the temperature of an insideair within a vehicle compartment is equal to or more than apredetermined reference inside air temperature, the frosting operationis started. After the inside air temperature of the vehicle interior iswarmed up to some degree, the defrosting operation can be started. Thus,during the defrosting operation, even in the use of means for decreasingthe heating capacity of the air in the user-side heat exchanger, theheat pump cycle can prevent the passenger from feeling unsatisfied withheating.

According to a 13th exemplar of the present invention, the heat pumpcycle of any one of first to 12th exemplars may be applied to an airconditioner for a vehicle. In this case, the heat pump cycle furtherincludes a frost formation determination portion for determining frostformation of the outdoor heat exchanger. Furthermore, the heat exchangefluid is air blown into the vehicle interior, the external heat sourceis a vehicle-mounted device generating heat in operation, the coolingfluid is a coolant for cooling the vehicle-mounted device, the user-sideheat exchanger is disposed in a casing forming therein an air passage,and an inside/outside air switching device for changing a ratio ofintroduction of inside air to outside air to be introduced into thecasing is disposed in the casing. Furthermore, the cooling fluid circuitswitching device performs switching to the cooling fluid circuit forflowing the cooling fluid to the heat-dissipation heat exchanger whenthe frost is determined to be formed at the outdoor heat exchanger bythe frost formation determination portion, and the inside/outside airswitching device increases the ratio of introduction of the inside airto the outside air as compared to before transfer to the defrostingoperation when the frost is determined to be formed at the outdoor heatexchanger by the frost formation determination portion.

Thus, even in the use of the means for decreasing the heating capacityof air in the user-side heat exchanger during the defrosting operation,the ratio of introduction of the volume of inside air having a hightemperature to that of outside air is increased, which can prevent thepassenger from feeling unsatisfied with heating.

According to a 14th exemplar of the present invention, the heat pumpcycle of one of first to 13th exemplars is applied to an air conditionerfor a vehicle, and the heat pump cycle further includes a frostformation determination portion configured to determine frost formationof the outdoor heat exchanger. In this case, the heat exchange fluid isair blown into the vehicle interior, the external heat source is avehicle-mounted device generating heat in operation, the cooling fluidis a coolant for cooling the vehicle-mounted device, the user-side heatexchanger is disposed in a casing forming therein an air passage, an airoutlet mode switching device for switching among air outlet modes bychanging opening/closing states of air outlets for blowing the air intothe vehicle interior is disposed in the casing, at least a foot airoutlet for blowing the air to a foot of a passenger is provided as theair outlet, the cooling fluid circuit switching device performsswitching to the cooling fluid circuit for flowing the cooling fluidinto the heat-dissipation heat exchanger when the frost is determined tobe formed at the outdoor heat exchanger by the frost formationdetermination portion, and the air outlet mode switching device performsswitching to the air outlet mode for blowing the air from the foot airoutlet when the frost is determined to be formed at the outdoor heatexchanger by the frost formation determination portion.

Further, even in the use of the means for decreasing the heatingcapacity of air in the user-side heat exchanger during the defrostingoperation, switching is performed to an air outlet mode for blowing theair from a foot air outlet. For example, as compared to the case wherethe air is blown toward the face of the passenger, the heat pump cyclecan prevent the passenger from feeling unsatisfied with heating.

According to a 15th exemplar of the present invention, the heat pumpcycle of any one of first to 14th exemplars is applied to an airconditioner for a vehicle, and the heat pump cycle further includes afrost formation determination portion configured to determine frostformation of the outdoor heat exchanger. In this case, the heat exchangefluid is air blown into the vehicle interior, the external heat sourceis a vehicle-mounted device generating heat in operation, the coolingfluid is a coolant for cooling the vehicle-mounted device, the user-sideheat exchanger is disposed in a casing for forming therein an airpassage, a blower for blowing air toward the vehicle interior isdisposed in the casing, the cooling fluid circuit switching deviceperforms switching to the cooling fluid circuit for flowing the coolingfluid into the heat-dissipation heat exchanger when the frost isdetermined to be formed at the outdoor heat exchanger by the frostformation determination portion, and the blower decreases an air blowingcapacity as compared to before the determination of the frost formation.

Moreover, even in the use of the means for decreasing the heatingcapacity of air in the user-side heat exchanger during the defrostingoperation, blower decreases its blowing capacity, which can prevent thepassenger from feeling unsatisfied with heating.

According to a 16th exemplar of the present invention, the heat pumpcycle of any one of first to 15th exemplars may be applied to an airconditioner for a vehicle, and the heat pump cycle may further include afrost formation determination portion for determining frost formation ofthe outdoor heat exchanger. In this case, the heat exchange fluid is airblown into the vehicle interior, the external heat source may be avehicle-mounted device generating heat in operation, the cooling fluidmay be a coolant for cooling the vehicle-mounted device, the frostformation determination portion may determines that the frost is formedat the outdoor heat exchanger when a vehicle speed is equal to or lessthan a predetermined reference speed and when a temperature of therefrigerant on an outlet side of the outdoor heat exchanger is equal toor less than 0° C., and the cooling fluid circuit switching device mayperform switching to a cooling fluid circuit for flowing the coolingfluid into the heat-dissipation heat exchanger when the frost isdetermined to be formed at the outdoor heat exchanger by the frostformation determination portion.

Specifically, when the frost is formed at the outdoor heat exchanger,the heat contained in a vehicle-mounted device can be effectively usedto defrost the outdoor heat exchanger. Further, a frost formationdetermination portion determines that the frost is formed at the outdoorheat exchanger when the speed of the vehicle is equal to or less than apredetermined reference vehicle speed and the temperature of refrigeranton the outlet side of the outdoor heat exchanger is equal to or lessthan 0° C. In this way, the appropriate determination of frost formationis performed taking into consideration the vehicle speed.

According to a 17th exemplar of the present invention, in the heat pumpcycle according to 16th exemplar, the frost formation determinationportion may determine that the frost is formed at the outdoor heatexchanger, when the speed of the traveling vehicle is equal to or lessthan the predetermined reference speed, and when the temperature of therefrigerant on the outlet side of the outdoor heat exchanger is equal toor less than 0° C. The term “traveling vehicle” means that a vehiclewhose speed is zero, that is, a stopping vehicle is not included.

According to an 18th exemplar of the present invention, the heat pumpcycle of one of exemplars 12 to 17 further includes a coolanttemperature detection portion configured to detect a temperature of thecoolant flowing into a vehicle-mounted device. In this case, the coolingfluid circuit switching device performs switching to the cooling fluidcircuit for flowing the cooling fluid into the heat-dissipation heatexchanger when a coolant temperature detected by the coolant temperaturedetection portion is equal to or more than the predetermined referencetemperature.

In this way, heat contained in the coolant is dissipated from theheat-dissipation heat exchanger, which can protect the vehicle-mounteddevice from overheat. The heat dissipated from the heat-dissipation heatexchanger can be transferred to the outdoor heat exchanger, and thenabsorbed in the refrigerant. In the normal operation of the heat pumpcycle, the indoor air can be effectively heated. As a result, theheating performance of the air conditioner for the vehicle can beimproved.

According to a 19th example of the present invention, in the heat pumpcycle of any one of first to 18th exemplars, the cooling fluidcirculation circuit stores therein the heat contained in the externalheat source when the cooling fluid circuit switching device performsswitching to the cooling fluid circuit for allowing the cooling fluid tobypass the heat-dissipation heat exchanger.

Thus, when the defrosting operation is not necessary, the cooling fluidcircuit switching device performs switching to a cooling fluid circuitfor allowing the flow of the cooling fluid to bypass theheat-dissipation heat exchanger, which can store the heat contained inthe external heat source, in the heat pump cycle. As a result, the heatstored during the defrosting operation can be used to complete thedefrosting in a short time.

For example, according to a 20th exemplar of the present invention, theheat pump cycle of the 19th exemplar is applied to an air conditionerfor a vehicle. In this case, the heat exchange fluid may be air blowninto the vehicle interior, the external heat source may be avehicle-mounted device generating heat in operation, the cooling fluidmay be a coolant for cooling the vehicle-mounted device, and the coolingfluid circulation circuit may store heat dissipated from thevehicle-mounted device in the coolant when the cooling fluid circuitswitching device performs switching to the cooling fluid circuit forallowing the cooling fluid to bypass the heat-dissipation heatexchanger.

According to a 21st exemplar of the present invention, the heat pumpcycle of 19th exemplar is applied to an air conditioner for a vehicle.In this case, the heat exchange fluid may be air blown into the vehicleinterior, the external heat source may be a heating element forgenerating heat by being supplied with power, the cooling fluid may be acoolant for cooling the heating element, and the cooling fluidcirculation circuit may store the heat dissipated from the heatingelement in the coolant when the cooling fluid circuit switching deviceperforms switching to the cooling fluid circuit for allowing the coolingfluid to bypass the heat-dissipation heat exchanger.

According to a 22nd exemplar of the present invention, the heat pumpcycle of 21st exemplar is applied to an air conditioner for a vehicle.In this case, the heat exchange fluid may be air blown into the vehicleinterior, a vehicle-mounted device generating heat in operation and aheating element for generating heat by being supplied with power may beprovided as the external heat source, the cooling fluid may be a coolantfor cooling the heating element and the vehicle-mounted device, and thecooling fluid circulation circuit may store the heat dissipated from atleast one of the vehicle-mounted device and the heating element in thecoolant when the cooling fluid circuit switching device performsswitching to the cooling fluid circuit for allowing the cooling fluid tobypass the heat-dissipation heat exchanger.

Furthermore, as in a 23rd exemplar of the present invention, the heatingelement may be an amount of generated heat therefrom controlled based onan outside air temperature. Therefore, it can restrict unnecessaryelectrical power from being consumed in the heating element.

According to a 24th exemplar of the present invention, the heat pumpcycle may further include: an outdoor unit bypass passage which causesthe refrigerant decompressed by the decompression device to bypass theoutdoor heat exchanger and to guide the refrigerant to a refrigerantoutlet side of the outdoor heat exchanger; and an outdoor-unit bypasspassage switching device configured to switch between a refrigerantcircuit for guiding the refrigerant decompressed by the decompressiondevice to the outdoor heat exchanger, and a refrigerant circuit forguiding the refrigerant decompressed by the decompression device towardthe outdoor unit bypass passage. In this case, in the defrostingoperation, the outdoor unit bypass passage switching device performsswitching to the refrigerant circuit for guiding the refrigerantdecompressed by the decompression device to the outdoor unit bypasspassage.

The outdoor unit bypass passage switching device performs switching to arefrigerant circuit for guiding the refrigerant decompressed bydecompression device to an outdoor unit bypass passage in the defrostingoperation, which can prevent the heat transmitted to the outdoor unitheat exchanger via the outer fins from being absorbed in the refrigerantflowing through the outdoor heat exchanger during the defrostingoperation.

Accordingly, the heat supplied from the external heat source can be usedmore effectively to defrost the outdoor heat exchanger during thedefrosting operation. For example, in application to an air conditionerfor a vehicle, the air can be heated by the user-side heat exchanger toachieve the heating of the vehicle interior.

According to a 25th exemplar of the present invention, the heat pumpcycle may further include: an indoor evaporator which exchanges heatbetween the refrigerant on a downstream side of the outdoor heatexchanger and the heat exchange fluid; an evaporator bypass passagewhich causes the refrigerant on the downstream side of the outdoor heatexchanger to bypass the indoor evaporator and to guide the refrigerantto a refrigerant outlet of the indoor evaporator; and an evaporatorbypass passage switching device configured to switch a refrigerantcircuit for guiding the refrigerant on the downstream side of theoutdoor heat exchanger to the indoor evaporator, and a refrigerantcircuit for guiding the refrigerant on the downstream side of theoutdoor heat exchanger to the evaporator bypass passage. In thedefrosting operation, the evaporator bypass passage switching deviceperforms switching to the refrigerant circuit for guiding therefrigerant on the downstream side of the outdoor heat exchanger to theindoor evaporator.

Thus, during the defrosting operation, the evaporator bypass passageswitching device guides the refrigerant on the downstream side of theoutdoor heat exchanger to an indoor evaporator side, so that the indoorevaporator can cool the heat exchange fluid by a heat absorption effectwhen the refrigerant is evaporated. For example, in application to theair conditioner for a vehicle, a dehumidification heating operation canbe achieved in which the air cooled by the indoor evaporator is heatedagain by the user-side heat exchanger.

According to a 26th exemplar of the present invention, the heat pumpcycle may be applied to an air conditioner for a vehicle. In this case,the heat exchange fluid is air blown into the vehicle interior, theuser-side heat exchanger is disposed in a casing for forming therein anair blowing passage, and in the casing, an auxiliary heater is providedfor heating the air blown into the vehicle interior using as a heatingsource, at least one of a heating fluid heated by a vehicle-mounteddevice that generates heat in operation, and a heating element thatgenerates heat by being supplied with power.

Thus, even when the heating capacity of the user-side heat exchanger forthe air is reduced by decreasing the refrigerant discharge capacity ofthe compressor during the defrosting operation, the air can be heated byan auxiliary heater. This arrangement can suppress the reduction intemperature of the air blown into the vehicle interior and thus canprevent the passenger from feeling unsatisfied with heating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall schematic diagram showing refrigerant flow in aheating operation of a heat pump cycle according to a first embodiment.

FIG. 2 is an overall schematic diagram showing refrigerant flow in adefrosting operation of the heat pump cycle according to the firstembodiment.

FIG. 3 is an overall schematic diagram showing refrigerant flow in awaste heat collecting operation of the heat pump cycle according to thefirst embodiment.

FIG. 4 is an overall schematic diagram showing refrigerant flow in acooling operation of the heat pump cycle according to the firstembodiment.

FIG. 5 is a schematic diagram showing a detail structure of an indoorair conditioning unit according to the first embodiment.

FIG. 6 is an overall schematic diagram showing refrigerant flow in aheating operation of a heat pump cycle according to a second embodiment.

FIG. 7 is an overall schematic diagram showing refrigerant flow in adefrosting operation of a heat pump cycle according to a thirdembodiment.

FIG. 8 is an overall schematic diagram showing refrigerant flow in adefrosting operation of a heat pump cycle according to a fourthembodiment.

FIG. 9 is an overall schematic diagram showing refrigerant flow in adefrosting operation of a heat pump cycle according to a fifthembodiment.

FIG. 10 is a perspective view of a heat exchanger structure according toa sixth embodiment.

FIG. 11 is an exploded perspective view of the heat exchanger structureaccording to the sixth embodiment.

FIG. 12 is a cross-sectional view taken along the line A-A in FIG. 10.

FIG. 13 is an exemplary perspective view for explaining the flow ofrefrigerant and the flow of coolant in the heat exchanger structureaccording to the sixth embodiment.

FIG. 14 is a flowchart showing a control flow of a vehicle interiorlinkage control according to a seventh embodiment.

FIG. 15 is a flowchart showing another control flow of the vehicleinterior linkage control according to the seventh embodiment.

FIG. 16 is a flowchart showing another control flow of the vehicleinterior linkage control according to the seventh embodiment.

FIG. 17 is a flowchart showing another control flow of the vehicleinterior linkage control according to the seventh embodiment.

FIG. 18 is an overall schematic diagram showing refrigerant flow in adefrosting operation of a heat pump cycle according to an eighthembodiment.

FIG. 19 is an overall schematic diagram showing refrigerant flow in adefrosting operation of a heat pump cycle according to a ninthembodiment.

FIG. 20 is an overall schematic diagram showing refrigerant flow in adefrosting operation of a heat pump cycle according to a tenthembodiment.

FIG. 21 is an overall schematic diagram showing refrigerant flow in adefrosting operation of a heat pump cycle according to an eleventhembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

Referring to FIGS. 1 to 5, a first embodiment of the present inventionwill be described below. In this embodiment of the present invention, aheat pump cycle 10 is applied to an air conditioner 1 for a vehicle ofthe so-called hybrid car, which can obtain a driving force for travelingfrom an internal combustion engine (engine) and an electric motor MG fortraveling. FIG. 1 shows an entire configuration diagram of the airconditioner 1 for the vehicle of this embodiment.

The hybrid car can perform switching between a traveling state in whichthe vehicle travels obtaining the driving force from both engine andelectric motor MG for traveling by operating or stopping the engineaccording to a traveling load on the vehicle or the like, and anothertraveling state in which the vehicle travels obtaining the driving forceonly from the electric motor MG for traveling by stopping the engine.Thus, the hybrid car can improve the fuel efficiency as compared tonormal cars obtaining a driving force for traveling only from theengine.

The heat pump cycle 10 in the air conditioner 1 for the vehicle servesto heat or cool the air in the vehicle compartment to be blown into thevehicle interior as a space for air conditioning. Thus, the heat pumpcycle 10 can switch between refrigerant flow paths to thereby perform aheating operation (heater operation) and a cooling operation (cooleroperation). The heating operation is adapted to heat the vehicleinterior by heating the air in the vehicle compartment as a heatexchange fluid as a normal operation. The cooling operation is adaptedto cool the vehicle interior by cooling the air blown into the vehiclecompartment.

Then, the heat pump cycle 10 can also perform a defrosting operation formelting and removing frost formed at an outdoor heat exchanger 16serving as an evaporator for evaporating refrigerant in the heatingoperation, and a waste heat collecting operation for absorbing heatcontained in the electric motor MG for traveling as the external heatsource, in the refrigerant in the heating operation. In the entireconfiguration diagrams of the heat pump cycle 10 shown in FIGS. 1 to 4,the flow of refrigerant in each operation is designated by a solidarrow.

The heat pump cycle 10 of this embodiment employs a normal flon-basedrefrigerant as a refrigerant, and forms a subcritical refrigerationcycle whose high-pressure side refrigerant pressure does not exceed thecritical pressure of the refrigerant. Into the refrigerant, arefrigerant oil for lubricating a compressor 11 is mixed, and a part ofthe refrigerant oil circulates through the cycle together with therefrigerant.

First, the compressor 11 is positioned in an engine room, and is tosuck, compress, and discharge the refrigerant in the heat pump cycle 10.The compressor is an electric compressor which drives a fixeddisplacement compressor 11 a having a fixed discharge capacity by use ofan electric motor 11 b. Specifically, various types of compressionmechanisms, such as a scroll type compression mechanism, or a vanecompression mechanism, can be employed as the fixed displacementcompressor 11 a.

The electric motor 11 b is one whose operation (number of revolutions)is controlled by a control signal output from an air conditioningcontroller to be described later. The motor 11 b may use either an ACmotor or a DC motor. The control of the number of revolutions of themotor changes a refrigerant discharge capacity of the compressionmechanism 11. Thus, in this embodiment, the electric motor 11 b servesas a discharge capacity changing portion of the compressor 11.

A refrigerant discharge port of the compressor 11 is coupled to arefrigerant inlet side of an indoor condenser 12 as a user-side heatexchanger. The indoor condenser 12 is disposed in a casing 31 of anindoor air conditioning unit 30 of the air conditioner 1 for thevehicle. The indoor condenser 12 is a heat exchanger for heating thatexchanges heat between a high-temperature and high-pressure refrigerantflowing therethrough and the air to be blown into the vehiclecompartment and having passed through an indoor evaporator 20 describedlater. The detailed structure of the indoor air conditioning unit 30will be described later.

A fixed throttle 13 for heating is coupled to a refrigerant outlet sideof the indoor condenser 12. The fixed throttle 13 serves as adecompression device for the heating operation that decompresses andexpands the refrigerant flowing from the indoor condenser 12 in theheating operation. The fixed throttle 13 for heating can use an orifice,a capillary tube, and the like. The outlet side of the fixed throttle 13for heating is coupled to the refrigerant inlet side of the outdoor heatexchanger 16.

A bypass passage 14 for the fixed throttle 13 is coupled to therefrigerant outlet side of the indoor condenser 12. The bypass passage14 causes a refrigerant flowing from the indoor condenser 12 to bypassthe fixed throttle 13 for heating and guides the refrigerant into theoutdoor heat exchanger 16. An opening/closing valve 15 a for opening andclosing the bypass passage 14 for the fixed throttle is disposed in thebypass passage 14 for the fixed throttle. The opening/closing valve 15 ais an electromagnetic valve whose opening and closing operations arecontrolled by a control voltage output from the air conditioningcontroller.

The loss in pressure caused when the refrigerant passes through theopening/closing valve 15 a is extremely small as compared to the losscaused in pressure when the refrigerant passes through the fixedthrottle 13. Thus, when the opening/closing valve 15 a is opened, therefrigerant flowing out of the indoor condenser 12 flows into theoutdoor heat exchanger 16 via the bypass passage 14 for the fixedthrottle. In contrast, when the opening/closing valve 15 a is closed,the refrigerant flows into the outdoor heat exchanger 16 via the fixedthrottle 13 for heating.

Thus, the opening/closing valve 15 a can switch between the refrigerantflow paths of the heat pump cycle 10. The opening/closing valve 15 a ofthis embodiment serves as a refrigerant flow path switching device.Alternatively, as such a refrigerant flow path switching device, anelectric three-way valve or the like may be provided for switchingbetween a refrigerant circuit for coupling the outlet side of the indoorcondenser 12 to the inlet side of the fixed throttle 13 for heating, andanother refrigerant circuit for coupling the outlet side of the indoorcondenser 12 and the inlet side of the bypass passage 14 for the fixedthrottle.

The outdoor heat exchanger 16 is to exchange heat between thelow-pressure refrigerant flowing therethrough and an outside air blownfrom a blower fan 17. The outdoor heat exchanger 16 is a heat exchangerdisposed in an engine room, and which serves as an evaporator forevaporating the low-pressure refrigerant to exhibit a heat absorptioneffect in the heating operation, and also as a radiator for dissipatingheat from the high-pressure refrigerant in the cooling operation.

The blower fan 17 is an electric blower whose operating ratio, that is,whose number of revolutions (volume of air) is controlled by a controlvoltage output from the air conditioning controller. The outdoor heatexchanger 16 of this embodiment is integral with a radiator 43 to bedescribed later, for exchanging heat between the coolant for cooling theelectric motor MG for traveling and the outside air blown from theblower fan 17.

The blower fan 17 of this embodiment serves as an outdoor blower forblowing the outside air toward both the outdoor heat exchanger 16 andthe radiator 43. The detailed structures of the outdoor heat exchanger16 and the radiator 43 (hereinafter referred to as a “heat exchangerstructure 70”) which are integral with each other will be described indetail below.

The outlet side of the outdoor heat exchanger 16 is coupled to anelectric three-way valve 15 b. The three-way valve 15 b has itsoperation controlled by a control voltage output from the airconditioning controller. The three-way valve 15 b serves as therefrigerant flow path switching device together with the aboveopening/closing valve 15 a.

More specifically, in the heating operation, the three-way valve 15 bperforms switching to the refrigerant flow path for coupling the outletside of the outdoor heat exchanger 19 to the inlet side of anaccumulator 18 to be described later. In contrast, in the coolingoperation, the three-way valve 15 b performs switching to therefrigerant flow path for coupling the outlet side of the outdoor heatexchanger 16 to the inlet side of a fixed throttle 19 for cooling.

The fixed throttle 19 for cooling serves as decompression device for thecooler operation (cooling operation) for decompressing and expanding therefrigerant flowing from the outdoor heat exchanger 16 in the coolingoperation. The fixed throttle 19 has the same basic structure as that ofthe above fixed throttle 13 for heating. The outlet side of the fixedthrottle 19 for cooling is coupled to the refrigerant inlet side of anindoor evaporator 20.

The indoor evaporator 20 is disposed on the upstream side of the airflow with respect to the indoor condenser 12 in the casing 31 of theindoor air conditioning unit 30. The indoor evaporator 20 is a heatexchanger for cooling that exchanges heat between the vehicle indoor airand the refrigerant flowing therethrough to thereby cool the air withinthe vehicle interior. A refrigerant outlet side of the indoor evaporator20 is coupled to an inlet side of the accumulator 18.

Thus, a refrigerant flow path for allowing the refrigerant to flow fromthe three-way valve 15 b to the inlet side of the accumulator 18 in theheating operation serves as an evaporator bypass passage 20 a forallowing the refrigerant on the downstream side of the outdoor heatexchanger 16 to bypass the indoor evaporator 20. The three-way valve 15b serves as evaporator bypass passage switching device for switchingbetween a refrigerant circuit for guiding the refrigerant on thedownstream side of the outdoor heat exchanger 16 to the indoorevaporator 20, and another refrigerant circuit for guiding therefrigerant on the downstream side of the outdoor heat exchanger 16 tothe evaporator bypass passage 20 a.

The accumulator 18 is a gas-liquid separator for the low-pressure siderefrigerant that separates the refrigerant flowing thereinto into liquidand gas phases, and which stores therein the excessive refrigerantwithin the cycle. A vapor-phase refrigerant outlet of the accumulator 18is coupled to a suction side of the compressor 11. Thus, the accumulator18 serves to suppress the suction of the liquid-phase refrigerant intothe compressor 11 to thereby prevent the compression of the liquid inthe compressor 11.

Next, the indoor air conditioning unit 30 will be described below usingFIG. 5. FIG. 5 shows an enlarged detailed configuration diagram,representing the indoor air conditioning unit 30 shown in FIGS. 1 to 4.The indoor air conditioning unit 30 is disposed inside a gauge board(instrument panel) at the forefront of the vehicle compartment. The unit30 accommodates in a casing 31 serving as an outer envelope, a blower32, the above-mentioned indoor condenser 12, and the indoor evaporator20.

The casing 31 forms an air passage communicating with the vehiclecompartment, through which air is blown into the vehicle interior. Thecasing 31 is formed of resin (for example, polypropylene) having somedegree of elasticity, and excellent strength. An inside/outside airswitch 33 for switching between the air (inside air) in the vehicleinterior and the outside air to introduce the selected air is disposedon the most upstream side of the vehicle-interior air flow in the casing31.

The inside/outside air switch 33 is an inside/outside air switchingdevice for switching between suction port modes by continuouslyadjusting the opening areas of an inside air inlet for introducing theinside air into the casing 31 and an outside air inlet for introducingthe outside air thereinto by an inside/outside air switching door tothereby continuously change the ratio of introduction of the inside airto the outside air.

The inside/outside air switch 33 is provided with the inside air inletfor introducing the inside air into the casing 31, and the outside airinlet for introducing the outside air thereinto. The inside/outside airswitching door is positioned inside the inside/outside air switch 33 tocontinuously adjust the opening areas of the inside air inlet and theoutside air inlet to thereby change the ratio of volume of the insideair to that of the outside air. The inside/outside air switching door isdriven by an electric actuator (not shown) whose operation is controlledby a control signal output from an air conditioning controller.

The suction port modes switched by the inside/outside air switch 33includes an inside air mode for introducing the inside air into thecasing 31 by fully opening the inside air inlet, while completelyclosing the outside air inlet; an outside air mode for introducing theoutside air into the casing 31, while completely closing the inside airinlet and fully opening the outside air inlet; and an inside-outside airmixing mode for simultaneously opening the inside air inlet and theoutside air inlet.

A blower 32 for blowing the air sucked via the inside/outside air switch33 into the vehicle interior is disposed on the downstream side of theair flow of the inside/outside air switch 33. The blower 32 is anelectric blower which includes a centrifugal multiblade fan (siroccofan) driven by an electric motor, and whose number of revolutions(volume of air) is controlled by a control voltage output from the airconditioning controller.

The indoor evaporator 20 and the indoor condenser 12 are disposed on thedownstream side of the air flow of the blower 32, in that order withrespect to the flow of the air in the vehicle interior. In short, theindoor evaporator 20 is disposed on the upstream side in the flowdirection of the vehicle indoor air with respect to the indoor condenser12.

An air mix door 34 is disposed on the downstream side of the air flow inthe indoor evaporator 20 and on the upstream side of the air flow in theindoor condenser 12. The air mix door 34 adjusts the rate of volume ofthe air passing through the indoor condenser 12 among the air passingthrough the indoor evaporator 20. A mixing space 35 is provided on thedownstream side of the air flow in the indoor condenser 12 so as to mixthe air exchanging heat with the refrigerant and being heated at theindoor condenser 12 and the air bypassing the indoor condenser 12 andnot being heated.

An opening hole for blowing the conditioned air mixed in the mixingspace 35, into the vehicle interior as a space of interest to be cooledis disposed on the most downstream side of the air flow in the casing31. Specifically, the opening holes include a defroster opening hole 36a for blowing the conditioned air toward the inner side of a front glassof the vehicle, a face opening hole 36 b for blowing the conditioned airtoward the upper body of a passenger in the vehicle compartment, and afoot opening hole 36 c for blowing the conditioned air toward the footof the passenger.

The defroster opening hole 36 a, the face opening hole 36 b, and thefoot opening hole 36 c have the respective downstream sides of the airflows thereof connected to a defroster air outlet, a face air outlet,and a foot air outlet provided in the vehicle compartment via ductsforming respective air passages.

The air mix door 34 adjusts the rate of volume of air passing throughthe indoor condenser 12 to thereby adjust the temperature of conditionedair mixed in the mixing space 35, thus controlling the temperature ofthe conditioned air blown from each air outlet. That is, the air mixdoor 34 serves as a temperature adjustment device for adjusting thetemperature of the conditioned air blown into the vehicle interior.

In short, the air mix door 34 serves as heat exchanging amountadjustment device for adjusting the amount of heat exchanged between therefrigerant discharged from the compressor 11 and the air in the vehicleinterior in the indoor condenser 12 serving as the user-side heatexchanger. The air mix door 34 is driven by a servo motor (not shown)whose operation is controlled based on the control signal output fromthe air conditioning controller.

The defroster opening hole 36 a, the face opening hole 36 b, and thefoot opening hole 36 c have, at the respective upstream sides of the airflows thereof, a defroster door 37 a for adjusting an opening area ofthe defroster opening hole 36 a, a face door 37 b for adjusting anopening area of the face opening hole 36 b, and a foot door 37 c foradjusting an opening area of the foot opening hole 36 c, respectively.

The defroster door 37 a, the face door 37 b, and the foot door 37 cserve as air outlet mode changing device for changing theopening/closing state of each air outlet for blowing the air into thevehicle interior, and are driven by an electric actuator (not shown)whose operation is controlled based on a control signal output from theair conditioning controller.

The air outlet modes include a face mode for blowing air toward theupper half body of the passenger in the vehicle interior from the faceair outlet by fully opening the face air outlet, a bi-level mode forblowing air toward the upper half body and the foot of the passenger inthe vehicle interior by opening both the face air outlet and the footair outlet, and a foot mode for blowing air mainly from the foot airoutlet by fully opening the foot air outlet, while slightly opening thedefroster air outlet.

The passenger can manually operate switches on an operation panel to bedescribed later to thereby setting the defroster mode for blowing theair from the defroster air outlet toward the inner surface of the frontglass of the vehicle by fully opening the defroster air outlet.

Next, a coolant circulation circuit 40 will be described below. Thecoolant circulation circuit 40 is a cooling fluid circulation circuitfor cooling the electric motor MG for traveling by allowing the coolant(for example, ethylene glycol aqueous solution) as a cooling fluid tocirculate through a coolant passage formed in the above electric motorMG for traveling, which is one of the vehicle-mounted devices generatingheat in operation.

The coolant circulation circuit 40 is provided with a coolant pump 41,an electric three-way valve 42, the radiator 43, and a bypass passage 44for allowing the coolant to flow bypassing the radiator 43.

The coolant pump 41 is an electric pump for squeezing the coolant into acoolant passage formed within the electric motor MG for traveling in thecoolant circulation circuit 40, and whose number of revolutions (flowrate) is controlled by a control signal output from the air conditioningcontroller. Thus, the coolant pump 41 serves as a cooling capacityadjustment portion for adjusting the cooling capacity by changing theflow rate of the coolant for cooling the electric motor MG fortraveling.

A three-way valve 42 switches between a cooling fluid circuit forflowing the coolant into the radiator 43 by connecting the inlet side ofthe coolant pump 41 to the outlet side of the radiator 43, and anothercooling fluid circuit for flowing the coolant to bypass the radiator 43by connecting the inlet side of the coolant pump 41 to the outlet sideof a bypass passage 44. The three-way valve 42 whose operation iscontrolled by the control voltage output from the air conditioningcontroller serves as cooling fluid circuit switching device.

That is, as illustrated by a dashed arrow of FIG. 1 or the like, thecoolant circulation circuit 40 of this embodiment can perform switchingbetween the cooling fluid circuit for circulation of the coolant fromthe coolant pump 41, the electric motor MG for traveling, the radiator43, and the cooling pump 41 in that order, and the cooling fluid circuitfor circulation of the coolant from the coolant pump 41, the electricmotor MG for traveling, the bypass passage 44, and the coolant pump 41in that order.

Thus, when the three-way valve 42 performs switching to the coolingfluid circuit for allowing the coolant to bypass the radiator 43 duringthe operation of the electric motor MG for traveling, the coolant hasits temperature increased without dissipating its heat into the radiator43. That is, when the three-way valve 42 performs switching to thecooling fluid circuit for allowing the coolant to bypass the radiator43, the heat (heat generated) contained in the electric motor MG fortraveling is stored in the coolant.

The radiator 43 is a heat-dissipation heat exchanger that is disposed inan engine room, and which exchanges heat between the coolant and theoutside air blown from the blower fan 17. As mentioned above, theradiator 43 is integrally structured with the outdoor heat exchanger 16to form a heat exchanger structure 70.

Now, the details of the heat exchanger structure 70 will be describedbelow. Each of the outdoor heat exchanger 16 and the radiator 43 in thisembodiment is comprised of the so-called tank and tube heat exchangerwhich includes a plurality of tubes for allowing the refrigerant orcoolant to flow therethrough, and a pair of tanks for collection anddistribution which are positioned on both sides of the tubes and whichare designed to collect or distribute the refrigerant or coolant flowingthrough the tubes.

More specifically, the outdoor heat exchanger 16 includes a plurality ofthe refrigerant tubes 16 a for flowing the refrigerant therethrough.Further, the refrigerant tube 16 a is a flat tube having a flattenedcross section in the direction perpendicular to the longitudinaldirection. The respective the refrigerant tubes 16 a are laminated witha predetermined gap therebetween such that flat surfaces of the outersurfaces thereof are opposed to each other in parallel.

Thus, a heat-absorption air passage 16 b to flow the outside air blownfrom the blower fan 17 is formed around the refrigerant tubes 16 a, thatis, between the adjacent the refrigerant tubes 16 a.

The radiator 43 includes a plurality of cooling fluid tubes 43 a forallowing the coolant to flow therethrough, and having a flattened crosssection in the direction perpendicular to the longitudinal direction.Like the refrigerant tubes 16 a, the cooling fluid tubes 43 a arelaminated with a predetermined gap therebetween. A heat-dissipation airpassage 43 b to flow the outside air blown from the blower fan 17 isformed around the cooling fluid tubes 43 a, that is, between theadjacent cooling fluid tubes 43 a.

In this embodiment, the respective tanks for collection and distributionof the outdoor heat exchanger 16 and the radiator 43 are partially madeof the same material, and the heat-absorption air passage and theheat-dissipation air passage are provided with outer fins 50 made of thesame substance. The outer fins 50 are bonded to both tubes 16 a and 43a, so that the outdoor heat exchanger 16 and the radiator 43 areintegral with each other to form the heat exchanger structure 70.

The outer fin 50 in use is a corrugated fin formed by bending a thinmetal plate with excellent heat conductivity in a wave shape. A part ofthe outer fin 50 disposed in the heat-absorption air passage serves topromote the heat exchange between the refrigerant and the outside air,and another part thereof disposed in the heat-dissipation air passageserves to promote the heat exchange between the coolant and the outsideair.

Further, each outer fin 50 is bonded to both the refrigerant tube 16 aand the cooling fluid tube 43 a, which enables the heat transfer betweenthe refrigerant tubes 16 a and the cooling fluid tubes 43 a.

In this embodiment described above, the refrigerant tubes 16 a of theoutdoor heat exchanger 16, the cooling fluid tubes 43 a of the radiator43, the tanks for collection and distribution, and the outer fins 50 areall formed of an aluminum alloy, and integral with one another bybrazing. Further, in this embodiment, the radiator 43 is integral withthe outdoor heat exchanger 16 on the windward side in the flow directionX of the outside air blown by the blower fan 17.

Now, an electric control unit of this embodiment will be describedbelow. The air conditioning controller is comprised of the knownmicrocomputer including a CPU, an ROM, and an RAM, and peripheralcircuits thereof. The control unit controls the operation of each of theair conditioning controller 11, 15 a, 15 b, 17, 41, and 42 connected toits output by executing various operations and processing based on airconditioning control programs stored in the ROM.

A group of various sensors for control of air conditioning is coupled tothe input side of the air conditioning controller. The sensors includean inside air sensor serving as inside air temperature detection portionfor detecting a temperature of the vehicle interior, an outside airsensor for detecting a temperature of the outside air, a solar radiationsensor for detecting an amount of solar radiation in the vehicleinterior, and an evaporator temperature sensor for detecting atemperature of blown air from the indoor evaporator 20 (evaporatortemperature). And, the sensors also include a discharged refrigeranttemperature sensor for detecting a temperature of the refrigerantdischarged from the compressor 11, an outlet refrigerant temperaturesensor 51 for detecting a refrigerant temperature Te on the outlet sideof the outdoor heat exchanger 16, and a coolant temperature sensor 52serving as coolant temperature detection portion for detecting a coolanttemperature Tw of the coolant flowing into the electric motor MG fortraveling.

In this embodiment, the coolant temperature sensor 51 detects thecoolant temperature Tw of the coolant squeezed from the coolant pump 41.Alternatively, the coolant temperature Tw of the coolant sucked into thecoolant pump 41 may be detected.

An operation panel (not shown) disposed near an instrument board at thefront of the vehicle compartment is connected to the input side of theair conditioning controller. Operation signals are input from varioustypes of air conditioning operation switches provided on the operationpanel. Various air conditioning operation switches provided on the panelinclude an operation switch for the air conditioner for the vehicle, avehicle-interior temperature setting switch for setting the temperatureof the vehicle interior, and a selection switch for selecting anoperation mode.

The air conditioning controller includes a control portion forcontrolling the electric motor 11 b for the compressor 11, and theopening/closing valve 15 a and the like which are integral with eachother, and is designed to control the operations of these components. Inthe air conditioning controller of this embodiment, the structure(hardware and software) for controlling the operation of the compressor11 serves as a refrigerant discharge capacity control portion. Thestructure for controlling the operations of the respective devices 15 aand 15 b serving as the refrigerant flow path switching device serves asa refrigerant flow path control portion. The structure for controllingthe operation of the three-way valve 42 serving as the cooling fluidcircuit switching device for coolant serves as a cooling fluid circuitcontrol portion.

The air conditioning controller of this embodiment includes thestructure (a frost formation determination portion) for determiningwhether or not the frost is formed at the outdoor heat exchanger 16,based on a detection signal from the above sensor group for the airconditioning control. Specifically, when the speed of a travelingvehicle is equal to or less than a predetermined reference value (inthis embodiment, 20 km/h), and the refrigerant temperature Te on theoutlet side of the outdoor heat exchanger 16 is equal to or less than 0°C., the frost formation determination portion of this embodimentdetermines that the frost formation is caused at the outdoor heatexchanger 16.

The determination using the frost formation determination portion is notlimited thereto. Alternatively, for example, when the vehicle is stopped(specifically, the vehicle speed=0 km/h) with a vehicle system kept inoperation, and the refrigerant temperature Te on the outlet side of theoutdoor heat exchanger 16 is equal to or less than 0° C., the frostformation may be determined to be caused at the outdoor heat exchanger16.

Next, the operation of the air conditioner 1 for the vehicle with theabove arrangement in this embodiment will be described below. The airconditioner 1 for the vehicle of this embodiment can execute a heatingoperation for heating the vehicle interior, and a cooling operation forcooling the vehicle interior. In the heating operation, a defrostingoperation and a waste heat collecting operation can also be carried out.Now, each operation will be explained in the following.

(a) Heating Operation

The heating operation is started when the heating operation mode isselected by the selection switch with the operation switch of theoperation panel is turned on (ON). Then, in the heating operation, whenthe frost formation determination portion determines that the frost isformed at the outdoor heat exchanger 16, the defrosting operation isperformed. When the coolant temperature Tw detected by the coolanttemperature sensor 52 is equal to or more than the predeterminedreference temperature (in this embodiment, 60° C.), the waste heatcollecting operation is performed.

In the normal heating operation, the air conditioning controller closesthe opening/closing valve 15 a, and switches the three-way valve 15 b tothe refrigerant flow path for coupling the outlet side of the outdoorheat exchanger 16 to the inlet side of the accumulator 18. Further, thecontroller actuates the coolant pump 41 to squeeze the coolant in apredetermined flow rate, and switches the three-way valve 42 of thecoolant circulation circuit 40 to the refrigerant flow path for allowingthe coolant to bypass the radiator 43.

In this way, the heat pump cycle 10 is switched to the refrigerant flowpath for allowing the refrigerant to flow as illustrated by the solidarrow in FIG. 1. The cooling fluid circulation circuit 40 is alsoswitched to the cooling fluid flow path for allowing the refrigerant toflow as illustrated by the dashed arrow in FIG. 1.

The air conditioning controller with the above refrigerant flow path andcooling fluid circuit reads a detection signal from the sensor group forthe air conditioning control and an operation signal from the operationpanel. Based on the detection signal and the operation signal, a targetoutlet air temperature TAO is calculated as the target temperature ofthe air to be blown into the vehicle interior. Further, the operatingstates of various air conditioning control components connected to theoutput side of the air conditioning controller are determined based onthe calculated target outlet air temperature TAO and the detectionsignal from the sensor group.

For example, the refrigerant discharge capacity of the compressor 11,that is, a control signal output to the electric motor of the compressor11 is determined as follows. First, a target evaporator outlet airtemperature TEO of the indoor evaporator 20 is determined based on thetarget outlet air temperature TAO with reference to a control mappreviously stored in the air conditioning controller.

Based on a deviation between the target evaporator outlet airtemperature TEO and the blown air temperature from the indoor evaporator20 detected by the evaporator temperature sensor, the control signal tobe output to the electric motor of the compressor 11 is determined suchthat the blown air temperature of the air blown from the indoorevaporator 20 approaches the target evaporator outlet air temperatureTEO by use of a feedback control method.

The control signal to be output to the servo motor of the air mix door34 is determined based on the target outlet air temperature TAO, theblown air temperature of the indoor evaporator 20, and the temperatureof the refrigerant discharged from the compressor 11 detected by thedischarge refrigerant temperature sensor such that the temperature ofair blown into the vehicle interior becomes a desired temperature set bythe passenger using the vehicle indoor temperature setting switch.

During the normal heating operation, the defrosting operation, and thewaste heat collecting operation, the opening degree of the air mix door34 may be controlled such that the whole volume of air in the vehicleinterior blown from the blower 32 passes through the indoor condenser12.

A control signal to be output to an electric actuator of theinside/outside air switch 33 is determined with reference to a controlmap previously stored in the air conditioning controller. In thisembodiment, basically, an outside air mode for introducing the outsideair is given a higher priority. However, when the target outlet airtemperature TAO becomes an ultra-high temperature to require highheating performance, or in the defrosting operation, an inside air modefor introducing the inside air is selected.

Control signals to be output to an electric actuator of each of the airoutlet mode changing device 37 a to 37 c are determined with referenceto a control map previously stored in the air conditioning controller.In this embodiment, as the target outlet air temperature TAO increasesfrom a low-temperature range to a high-temperature range, the air outletmode is switched from the face mode to the bi-level mode, and then tothe foot mode in that order. Thus, in the heating operation, the footmode is apt to be selected.

Then, the control signals determined as described above are output tovarious air conditioning control components. Thereafter, until thestopping of the air conditioner for a vehicle is requested by theoperation panel, a control routine is repeated at every predeterminedcontrol cycle. The control routine includes a series of processes:reading of the detection signal and the operation signal, calculation ofthe target outlet air temperature TAO, determination of the operationstates of various air conditioning control components, and output of thecontrol voltage and the control signal in that order. Such repetition ofthe control routine is basically performed in other operation modes inthe same way.

In the heat pump cycle 10 during the normal heating operation, thehigh-pressure refrigerant discharged from the compressor 11 flows intothe indoor condenser 12. The refrigerant flowing into the indoorcondenser 12 exchanges heat with the vehicle interior air blown from theblower 32 through the indoor evaporator 20 to dissipate the heattherefrom, so that the vehicle interior air is heated.

The high-pressure refrigerant flowing from the indoor condenser 12 flowsinto the fixed throttle 13 for heating to be decompressed and expandedby the throttle because the opening/closing valve 15 a is closed. Thelow-pressure refrigerant decompressed and expanded by the fixed throttle13 for heating flows into an outdoor heat exchanger 16. The low-pressurerefrigerant flowing into the outdoor heat exchanger 16 absorbs heat fromthe outside air blown by the blower fan 17 to evaporate itself.

At this time, in the coolant circulation circuit 40, switching isperformed to the cooling fluid circuit for allowing the coolant tobypass the radiator 43, which prevents the coolant from dissipating heatto the refrigerant flowing through the outdoor heat exchanger 16, andalso prevents the coolant from absorbing heat from the refrigerantflowing through the outdoor heat exchanger 16. That is, the coolantnever has a thermal influence on the refrigerant flowing through theoutdoor heat exchanger 16.

Since the three-way valve 15 b is switched to the refrigerant flow pathconnecting the outlet side of the outdoor heat exchanger 16 to the inletside of the accumulator 18, the refrigerant flowing from the outdoorheat exchanger 16 flows into the accumulator 18 and is separated intoliquid and gas phases. The gas-phase refrigerant separated into by theaccumulator 18 is sucked by the compressor 11 and compressed again.

As mentioned above, in the normal heating operation, the air in thevehicle interior is heated by the indoor condenser 12 with heatcontained in the refrigerant discharged from the compressor 11, whichcan perform the heating operation of the vehicle interior.

(b) Defrosting Operation

Next, the defrosting operation will be described below. In refrigerationcycle devices for evaporating the refrigerant by exchanging heat betweenthe refrigerant and outside air in the outdoor heat exchanger 16, likethe heat pump cycle 10 of this embodiment, when a refrigerantevaporation temperature as one of the temperatures of the outdoor heatexchanger 16 (specifically, the temperature of an outer surface of theoutdoor heat exchanger 16, or the outdoor heat exchanger 16) becomesequal to or less than a frost formation temperature (specifically, 0°C.), the frost might be formed at the outdoor heat exchanger 16.

Such formation of the frost closes the heat-absorption air passage 16 bof the outdoor heat exchanger 16 with the frost, which drasticallyreduces the heat exchange capacity of the outdoor heat exchanger 16. Inthe heat pump cycle 10 of this embodiment, when the frost formation isdetermined to be caused at the outdoor heat exchanger 16 by the frostformation determination portion in the heating operation, the defrostingoperation is started.

In the defrosting operation, the air conditioning controller stops theoperation of the compressor 11, and also stops the operation of theblower fan 17. Thus, during the defrosting operation, the flow rate ofrefrigerant flowing into the outdoor heat exchanger 16 is decreased,which leads to a decrease in volume of outside air flowing into theheat-absorption air passage 16 b of the outdoor heat exchanger 16 andinto the heat-dissipation air passage 43 b of the radiator 43, ascompared to the normal heating operation.

The air conditioning controller switches the three-way valve 42 of thecoolant circulation circuit 40 to the cooling fluid circuit for allowingthe coolant to flow into the radiator 43 as indicated by the dashedarrow in FIG. 2. Thus, the coolant circulation circuit 40 is switched tothe cooling fluid circuit for flowing the refrigerant as indicated bythe dashed arrow in FIG. 2 without circulation of the refrigerantthrough the heat pump cycle 10.

Thus, the heat contained in the coolant flowing through the coolingfluid tubes 43 a of the radiator 43 is transferred to theheat-absorption air passages 16 b of the outdoor heat exchanger 16 viathe outer fins 50, whereby the defrosting operation of the outdoor heatexchanger 16 is carried out. That is, the defrosting is achieved whichcan effectively use the waste heat of the electric motor MG fortraveling.

(c) Waste Heat Collecting Operation

Next, the waste heat collecting operation will be described below.Preferably, in order to suppress the over heat of the electric motor MGfor traveling, the temperature of the coolant is maintained at apredetermined upper limit temperature or less. Further, in order toreduce the friction loss due to an increase in viscosity of oil forlubrication sealed into the electric motor MG for traveling, preferably,the temperature of the coolant is maintained at a predetermined lowerlimit temperature or more.

In the heat pump cycle 10 of this embodiment, when the coolanttemperature Tw is equal to or more than the predetermined referencetemperature (60° C. in this embodiment) during the heating operation,the waste heat collecting operation is performed. In the defrostingoperation, the three-way valve 15 b of the heat pump cycle 10 isperformed in the same way as in the normal heating operation, but thethree-way valve 42 of the coolant circulation circuit 40 is switched tothe cooling fluid circuit for flowing the coolant into the radiator 43as indicated by the dashed arrow in FIG. 3 in the same way as in thedefrosting operation.

Thus, as illustrated by the solid arrow in FIG. 3, the high-pressure andhigh-temperature refrigerant discharged from the compressor 11 heats theair in the vehicle interior at the indoor condenser 12, and is thendecompressed and expanded by the fixed throttle 13 for heating to flowinto the outdoor heat exchanger 16 in the same way as in the normalheating operation.

Since the three-way valve 42 is switched to the cooling fluid circuitfor flowing the coolant into the radiator 43, the low-pressurerefrigerant flowing into the outdoor heat exchanger 16 absorbs both theheat contained in the outside air blown by the blower fan 17 and theheat contained in the coolant and transmitted thereto via the outer fins50 to evaporate itself. Other actuations are the same as those in thenormal heating operation.

As described above, in the waste heat collecting operation, the air inthe vehicle interior is heated at the indoor condenser 12 with the heatof the refrigerant discharged from the compressor 11, which can performheating of the vehicle interior. At this time, the refrigerant absorbsnot only the heat contained in the outside air, but also the heatcontained in the coolant and transmitted thereto via the outer fins 50,which can achieve the heating of the vehicle interior effectively usingthe waste heat of the electric motor MG for traveling.

(d) Cooling Operation

The cooling operation is started when the cooling operation mode isselected by the selection switch with the operation switch of theoperation panel is turned on (ON). In the cooling operation, the airconditioning controller opens the opening/closing valve 15 a, andswitches the three-way valve 15 b to the refrigerant flow path forconnecting the outlet side of the outdoor heat exchanger 16 to the inletside of the fixed throttle 19 for cooling. Thus, the heat pump cycle 10is switched to the refrigerant flow path for flowing the refrigerant asindicated by the solid arrow in FIG. 4.

At this time, when the coolant temperature Tw is equal to or more thanthe reference temperature, the three-way valve 42 of the coolantcirculation circuit 40 is switched to the cooling fluid circuit forflowing the coolant into the radiator 43. In contrast, when the coolanttemperature Tw is less than the predetermined reference temperature, thethree-way valve 42 is switched to the cooling fluid circuit for allowingthe coolant to bypass the radiator 43. The flow of the coolant obtainedwhen the coolant temperature Tw is equal to or more than the referencetemperature is indicated by the dashed arrow in FIG. 4.

In the heat pump cycle 10 during the cooling operation, thehigh-pressure refrigerant discharged from the compressor 11 flows intothe indoor condenser 12, and exchanges heat with the air in the vehicleinterior blown from the blower 32 and having passed through the indoorevaporator 20 to dissipate heat therefrom. The high-pressure refrigerantflowing from the indoor condenser 12 flows into the outdoor heatexchanger 16 via the bypass passage 14 for the fixed throttle becausethe opening/closing valve 15 a is opened. The low-pressure refrigerantflowing into the outdoor heat exchanger 16 further radiates heat towardthe outside air blown by the blower fan 17.

Since the three-way valve 15 b is switched to the refrigerant flow pathfor connecting the outlet side of the outdoor heat exchanger 16 to theinlet side of the fixed throttle 19 for cooling, the refrigerant flowingfrom the outdoor heat exchanger 16 is decompressed and expanded by thefixed throttle 19 for cooling. The refrigerant flowing from the fixedthrottle 19 for cooling flows into the indoor evaporator 20, and absorbsheat from the air in the vehicle interior blown by the blower 32 toevaporate itself. In this way, the air in the vehicle interior can becooled.

The refrigerant flowing from the indoor evaporator 20 flows into theaccumulator 18, and is then separated into liquid and gas phases by theaccumulator. The gas-phase refrigerant separated into by the accumulator18 is sucked into and compressed by the compressor 11 again. Asmentioned above, during the cooling operation, the low-pressurerefrigerant absorbs heat from the air in the vehicle interior andevaporates itself at the indoor evaporator 20 to thereby cool the air inthe vehicle interior, which can perform cooling of the vehicle interior.

As described above, the air conditioner 1 for the vehicle in thisembodiment can perform switching among the refrigerant flow paths of theheat pump cycle 10, and among the cooling fluid circuits of the coolantcirculation circuit 40 to thereby carry out various operations. Further,in the defrosting operation of this embodiment, the waste heat of theelectric motor MG for traveling can be effectively used to defrost theoutdoor heat exchanger 16 as will be described later.

More specifically, in this embodiment, the heat-absorption air passage16 b of the outdoor heat exchanger 16 and the heat-dissipation airpassage 43 b of the radiator 43 are provided with the outer fins 50 madeof the same metal material to enable the heat transfer between therefrigerant tubes 16 a and the cooling fluid tubes 43 a. Thus, duringthe defrosting operation, the heat contained in the coolant can betransmitted to the outdoor heat exchanger 16 via the outer fins 50.

Therefore, this embodiment can suppress the loss in heat transfer ascompared to the related art cycle in which heat contained in the coolantis transmitted to the outdoor heat exchanger 16 via air, and thus caneffectively use the waste heat of the electric motor MG for travelingfor defrosting the outdoor heat exchanger 16. Moreover, this embodimentcan reduce the time for the defrosting operation.

During the defrosting operation, the operation of the compressor 11 isstopped and the flow rate of refrigerant flowing into the outdoor heatexchanger 16 is decreased (specifically, set to zero (0)) as compared tothe time before the defrosting operation, which can prevent the heattransmitted to the outdoor heat exchanger 16 via the outer fins 50 frombeing absorbed in the refrigerant flowing through the refrigerant tubes16 a. Thus, the waste heat of the electric motor MG for traveling can beused more effectively to defrost the outdoor heat exchanger 16 duringthe defrosting operation.

In other words, during the defrosting operation, the operation of thecompressor 11 is stopped to decrease the heating capacity for heatingthe air at the indoor condenser 12 (in this embodiment, such that theheating capacity is not exhibited), which decreases the amount of heatof the refrigerant absorbed in the outdoor heat exchanger 16. Thus, thewaste heat of the electric motor MG for traveling can be used moreeffectively to defrost the outdoor heat exchanger 16 in the defrostingoperation.

During the defrosting operation, the operation of the blower fan 17 isstopped to decrease the volume of outside air flowing into theheat-absorption air passages 16 b and the heat dissipation air passage43 b (specifically, set to zero (0)), which can prevent the heattransmitted to the outdoor heat exchanger 16 via the outer fins 50 frombeing absorbed in the outside air flowing through the heat-absorptionair passages 16 b and the heat-dissipation air passage 43 b. Thus, thewaste heat of the electric motor MG for traveling can be used moreeffectively to defrost the outdoor heat exchanger 16 in the defrostingoperation.

In the heat pump cycle 10 of this embodiment, during the normal heatingoperation, the three-way valve 42 of the coolant circulation circuit 40is switched to the cooling fluid circuit for allowing the coolant tobypass the radiator 43 to thereby store the heat (generated heat)contained in the electric motor MG for traveling, in the coolant. Thus,during the defrosting operation, the defrosting operation can becompleted by the stored heat in a short time.

In the heat exchanger structure 70 of this embodiment, the radiator 43is arranged on the windward side of the flow direction X of the outsideair blown by the blower fan 17 with respect to the outdoor heatexchanger 16. In other words, in the heat exchanger structure 70, theoutdoor heat exchanger 16 and the radiator 43 are arranged in seriessuch that the outside air flows from the radiator 43 to the outdoor heatexchanger 16.

Thus, the heat contained in the coolant can be transferred to theoutdoor heat exchanger 16 not only via the outer fins 50, but also viaair. That is, even when the blower fan 17 is stopped, the heat containedin the coolant can be transferred to the outdoor heat exchanger 16 byair pressure (ram air pressure) in the traveling direction of thetraveling vehicle via the outside air passing through the heat exchangerstructure 70. Thus, during the defrosting operation, the heat suppliedfrom the electric motor MG for traveling can be used more effectively todefrost the outdoor heat exchanger 16.

The frost formation determination portion included in the airconditioning controller of this embodiment determines that the frost isformed in the outdoor heat exchanger 16 when the vehicle speed is equalto or less than the reference vehicle speed, and when the refrigeranttemperature Te on the outlet side of the outdoor heat exchanger 16 isequal to or less than 0° C. Accordingly, the frost formation can beappropriately determined taking into consideration the vehicle speed.

That is, when the vehicle travels at low speed, the ram air pressurebecomes lower and the volume of outside air flowing into the engine roomis decreased. Thus, the volume of outside air flowing into each of theoutdoor heat exchanger 16 and the radiator 43 is decreased. Thus, in thedefrosting operation, the heat transferred to the outdoor heat exchanger16 via the outer fins 50 is prevented from being absorbed in the outsideair, which can achieve the effective defrosting.

Further, in the heat pump cycle 10 of this embodiment, when the coolanttemperature Tw detected by the coolant temperature sensor 52 is equal toor more than the reference temperature, the waste heat collectingoperation is performed by switching the three-way valve 42 to a coolingfluid circuit for flowing the coolant in the radiator 43. Thus, the heatcontained in the coolant is dissipated by the radiator 43, which canprotect the electric motor MG for traveling from over heat.

Additionally, in the waste heat collecting operation, the heatdissipated by the radiator 43 is transferred to the outdoor heatexchanger 16, and can be absorbed in the refrigerant, which can improvea coefficient of performance (COP) of the heat pump cycle 10, and thuscan effectively heat the air in the vehicle interior. As a result, theheating performance of the air conditioner 1 for the vehicle can beimproved.

In this embodiment, the three-way valve 42 is switched to the coolingfluid circuit for flowing the coolant into the radiator 43 to performthe waste heat collecting operation based on the reference temperatureof 60° C. The reference temperature can be determined by the heatexchange performance or the like of the outdoor heat exchanger 16 andthe like.

For example, when WW (g) is the weight of the coolant in the coolantcirculation circuit 40, WG (g) is the amount of frost formed in theoutdoor heat exchanger 16, TR (° C.) is the temperature of air blownfrom the outdoor heat exchanger 16, the amount of storage heat Qststored in the coolant in the coolant circulation circuit 40 isrepresented by the following formula F1, and the amount of heat requiredfor defrosting (hereinafter referred to as a “defrosting heat amount”)Qdf is represented by the following formula F2:

Qst=WW×Specific Heat of Coolant×(Tw−TR)  (F1)

Qdf=WG×Latent Heat of Vaporization of Water−Specific Heat of Water×

TR+Outdoor Heat Exchanger 16×Heat Capacity×TR+Amount of Heat

Dissipated into Air  (F2)

in which the storage heat amount Qst needs to exceed the defrosting heatamount Qdf in order to ensure the defrosting of the outdoor heatexchanger 16.

Further, when the heat capacity of the outdoor heat exchanger 16 and theamount of heat dissipated into air in the formula F2 are considered asignorable ones, the minimum defrosting heat amount Qdf2 required to meltthe frost formed at the outdoor heat exchanger 16 is represented by thefollowing formula F3:

Qdf2=WG×Latent Heat of Vaporization of Water−Specific Heat ofWater×TR  (F3)

Therefore, in order to perform the defrosting, at least the followingformula F4 has to be satisfied:

Qst>Qdf2  (F4)

Substitution of the formulas (F1) and (F3) into the above formula (F4)can yield the following formula (F5):

Tw>TR+(WG×Latent Heat of Vaporization of Water−Specific Heat of

Water×TR)/(WW×Specific Heat of Coolant)  (F5)

Therefore, the temperature Tw satisfying the above formula F5 may bedetermined as the reference temperature.

In other words, the heat pump cycle of this embodiment includes coolanttemperature detection portion (coolant temperature sensor 52) fordetecting the coolant temperature Tw of the coolant flowing into thevehicle-mounted device (electric motor MG for traveling) generating heatin operation, and outdoor blown air temperature detection portion fordetecting the air temperature TR of air blown from the outdoor heatexchanger 16. The cooling fluid circuit switching device (three-wayvalve 42) may perform switching to the cooling fluid circuit forallowing the cooling fluid (coolant) to flow into the heat-dissipationheat exchanger (radiator 43) when the coolant temperature TW detected bythe coolant temperature detection portion (coolant temperature sensor52) and the air temperature TR detected by the outdoor blown airtemperature detection portion satisfy the following relationship:

Tw>TR+(WG×Latent Heat of Vaporization of Water−Specific Heat of

Water×TR)/(WW×Specific Heat of Coolant).

In the heat pump cycle 10 of this embodiment, during the heatingoperation (heater operation), the flow direction of refrigerant flowingthrough the refrigerant tubes 16 a of the outdoor heat exchanger 16 isthe same as that of refrigerant flowing through the refrigerant tubes 16a during the cooling operation (cooler operation). As viewed from theflow direction of outside air, the positional relationship between aheat exchange region on a refrigerant inlet side of the outdoor heatexchanger 16 and a heat exchange region on a refrigerant outlet sidethereof does not change between the heating operation and the coolingoperation. Therefore, the positional relationship between thetemperature distribution of the heat exchange region of the outdoor heatexchanger 16 and the temperature distribution of the heat exchangeregion of the heat disspation heat exchanger 43 does not change.

That is, the outdoor heat exchanger 16 and the heat disspation heatexchanger 43 are macroscopically regarded as one heat exchangerstructure 70. In that case, during the cooling operation for dissipatingheat from the refrigerant at the outdoor heat exchanger 16, a heatexchange region on the refrigerant inlet side of the outdoor heatexchanger 16 for flowing the refrigerant having a superheat degree at arelatively high temperature can be superimposed in the flow direction ofthe outside air, on a heat exchange region on the cooling fluid inletside of the heat disspation heat exchanger 43 for flowing the coolingfluid at a relatively high temperature. Further, a heat exchange regionon the refrigerant outlet side of the outdoor heat exchanger 16 forflowing the refrigerant having a superheat degree at a relatively lowtemperature can be superimposed in the flow direction of the outsideair, on a heat exchange region on the cooling fluid outlet side of theheat disspation heat exchanger 43 for flowing the cooling fluid at arelatively low temperature. With this arrangement, the flow of therefrigerant through the outdoor heat exchanger 16 and the flow of thecooling fluid through the heat disspation heat exchanger 43 can be madeparallel to achieve the effective heat exchange.

Further, in the heating operation for evaporating the refrigerant at theoutdoor heat exchanger 16, a heat exchange region on the refrigerantinlet side of the outdoor heat exchanger 16 for flowing the refrigerantat a relatively low temperature can be superimposed in the flowdirection of the outside air, on a heat exchange region on the coolingfluid inlet side of the heat disspation heat exchanger 43 for flowingthe cooling fluid at a relatively high temperature. As a result, thefrost can be effectively prevented from being formed in the heatexchange region on the refrigerant inlet side of the outdoor heatexchanger 16 for allowing the refrigerant to flow therethrough at arelative low temperature.

Second Embodiment

Unlike the first embodiment, in this embodiment, as shown in the entireconfiguration diagram of FIG. 6, the indoor condenser 12 is removed, anda brine circuit 60 is provided for circulating brine, that is, a heatingfluid by way of example. FIG. 6 is an entire configuration diagramshowing refrigerant flow paths and the like during the heating operationin this embodiment, in which the flow of refrigerant in the heat pumpcycle 10 is indicated by the solid line, and the flow of coolant in thecoolant circulation circuit 40 is indicated by the dashed arrow.

In FIG. 6, the same or equivalent part as that of the first embodimentis designated by the same reference character. The same goes for thefollowing other drawings.

Brine in this embodiment is a heating fluid for transferring heatcontained in the refrigerant discharged from the compressor 11 to theair blown into the vehicle interior. Like the coolant as the coolingfluid, an ethylene glycol aqueous solution can be used. The brinecircuit 60 includes a brine pump 61, a brine-refrigerant heat exchanger62, and a heater core 63.

The brine pump 61 is an electric pump for squeezing the brine into theheater core 63 of the brine-refrigerant heat exchanger 62. The brinepump 61 has the same basic structure as that of the coolant pump 41 ofthe coolant circulation circuit 40. The brine-refrigerant heat exchanger62 is a heat exchanger for exchanging heat between the refrigerantdischarged from the compressor 11 and flowing through a refrigerantpassage 62 b, and the brine flowing through the brine passage 62 a.

Specifically, the brine-refrigerant heat exchanger 62 can employ adouble tube type heat exchanger structure comprised of an outer pipeforming the brine passage 62 a, and an inner pipe disposed in the outerpipe for forming the refrigerant passage 62 b. Alternatively, therefrigerant passage 62 b may be formed as the outer pipe, and the brinepassage 62 a may be formed as the inner pipe. The refrigerant pipeforming the refrigerant passage 62 b and the refrigerant pipe formingthe brine passage 62 a can be bonded together by brazing to form theheat exchanging structure and the like.

The heater core 63 is disposed in the casing 31 of the indoor airconditioning unit 30 of the air conditioner 1 for the vehicle. Theheater core 63 is a heat exchanger for heating that exchanges heatbetween the brine passing therethrough and the vehicle-interior airhaving passed through the indoor evaporator 20. Thus, the heater core 63of this embodiment serves as the user-side heat exchanger, which is thesame as the indoor condenser 12. The structures and operations of othercomponents in this embodiment are the same as those in the firstembodiment.

Accordingly, even the operation of the air conditioner 1 for the vehicleof this embodiment can provide the same effects as those of the firstembodiment. Further, since the brine circuit 60 is provided in thisembodiment, the heating capacity of the heater core 63 can be easilyadjusted by changing a coolant squeezing capacity of the brine pump 61.

Like the coolant, the brine in the brine pump 61 can also store the heatcontained in the refrigerant discharged from the compressor 11 duringthe normal heating operation. Thus, even when the compressor 11 isstopped in the defrosting operation, the brine pump 61 can be operatedto perform an auxiliary heating operation of the vehicle interior.

Third Embodiment

Unlike the heat pump cycle 10 of the first embodiment, as shown in theentire configuration diagram of FIG. 7, in this embodiment, an outdoorunit bypass passage 64 is added for allowing the refrigerant flowingfrom the fixed throttle 13 for heating or the bypass passage 14 for thefixed throttle to bypass the outdoor heat exchanger 16. And, anopening/closing valve 15 c is further added for opening and closing theoutdoor unit bypass passage 64.

FIG. 7 is an entire configuration diagram showing refrigerant flow pathsduring the defrosting operation in this embodiment, in which the flow ofrefrigerant in the heat pump cycle 10 is indicated by a solid line, andthe flow of coolant in the coolant circulation circuit 40 is indicatedby a dashed arrow.

The opening/closing valve 15 c has the same basic structure as that ofthe opening/closing valve 15 a disposed in the bypass passage 14 for thefixed throttle. The loss in pressure generated in the refrigerantpassing through the opening/closing valve 15 c when the opening/closingvalve 15 c is opened is much smaller than the loss in pressure generatedin the refrigerant when the refrigerant passes through the outdoor heatexchanger 16.

Thus, when the opening/closing valve 15 c is opened, most of therefrigerant flowing from the fixed throttle 13 for heating or the bypasspassage 14 for the fixed throttle flows into the outdoor unit bypasspassage 64, and hardly flows into the outdoor heat exchanger 16.

In this embodiment, in the defrosting operation, the air conditioningcontroller opens the opening/closing valve 15 c without stopping theoperation of the compressor 11, and in other operation modes, theopening/closing valve 15 c is closed. Thus, during the defrostingoperation, the flow rate of refrigerant flowing into the outdoor heatexchanger 16 is decreased. The structures and operations of othercomponents in this embodiment are the same as those in the firstembodiment.

Thus, even the operation of the air conditioner 1 for the vehicle ofthis embodiment can provide the same effects as those of the firstembodiment. Further, since the operation of the compressor 11 is notstopped during the defrosting operation in this embodiment, the indoorcondenser 12 can exhibit the heating capacity of the air with the heatcontained in the refrigerant discharged from the compressor 11 tothereby perform the heating operation of the vehicle interior.

At this time, in the defrosting operation, the flow direction ofrefrigerant passing through the refrigerant tubes 16 a of the outdoorheat exchanger 16 is the same as that in the heating operation (normaloperation), which enables quick transfer from the normal operation tothe defrosting operation, or from the defrosting operation to the normaloperation. As a result, the defrosting time can be further reduced.

As viewed from the flow direction of the outside air, the positionalrelationship between the heat exchange region on the refrigerant inletside of the outdoor heat exchanger 16 and the heat exchange region onthe refrigerant outlet side thereof does not change with respect to theheat exchange region of the radiator 43, which can suppress largefluctuations in amount of heat transferred between the refrigerantflowing through the refrigerant tubes 16 a of the outdoor heat exchanger16 and the cooling fluid flowing through the cooling fluid tubes 43 a ofthe radiator 43.

That is, when the heat exchange is performed between the refrigeranttubes 16 a of the outdoor heat exchanger 16 via the outer fins 50 andthe cooling fluid tubes 43 a of the radiator 43, the relationshipbetween the flow of the entire refrigerant in the outdoor heat exchanger16 and the flow of the entire coolant in the radiator 43 might bechanged from the opposite to the parallel, or from the parallel to theopposite in the related art. However, this embodiment can avoid such asituation.

As a result, the heat pump cycle of this embodiment can suppress thelarge fluctuations in amount of heat transfer between the refrigerantflowing through the refrigerant tubes 16 a and the cooling fluid flowingthrough the cooling fluid tubes 43 a, thus improving the flexibility indesign of the outdoor heat exchanger 16 and the radiator 43.

Fourth Embodiment

This embodiment has the substantially same cycle structure as that ofthe heat pump cycle 10 of the third embodiment, but has a differentcontrol form of the air conditioning controller in the defrostingoperation, which will be described below by way of example.

Specifically, in this embodiment, during the defrosting operation, theair conditioning controller opens the opening/closing valve 15 a and theopening/closing valve 15 c without stopping the operation of thecompressor 11, and switches the three-way valve 15 b to the refrigerantflow path for connecting the outlet side of the outdoor heat exchanger16 (specifically, the outlet side of the outdoor unit bypass passage 64)to the inlet side of the fixed throttle 19 for cooling.

Thus, in this embodiment, in the defrosting operation, as shown in FIG.8, the heat pump cycle 10 is switched to the cycle for circulating therefrigerant from the compressor 11, to the indoor condenser 12 (outdoorunit bypass passage 64), the fixed throttle 19 for cooling, the indoorevaporator 20, the accumulator 18, and the compressor 11 in that order.

The refrigerant flowing from the fixed throttle 19 for cooling takeslatent heat of vaporization from the air upon evaporating at the indoorevaporator 20, so that the air can be cooled. Then, when the refrigerantdischarged from the compressor 11 dissipates heat at the indoorcondenser 12, the cooled air is re-heated. The structures and operationsof other components in this embodiment are the same as those in thefirst embodiment.

Thus, even the operation of the air conditioner 1 for the vehicle ofthis embodiment can provide the same effects as those of the thirdembodiment. Further, in this embodiment, the air cooled by evaporatingthe refrigerant at the indoor evaporator 20 can be heated again by theindoor condenser 12 in the defrosting operation, which can achieve thedefrosting and heating of the vehicle interior.

Fifth Embodiment

Unlike the heat pump cycle 10 of the first embodiment, as shown in theentire configuration diagram of FIG. 9, in this embodiment, a shutterdevice (passage interruption means) is added for opening or closing aninflow route for flowing the outside air into the radiator 43, by way ofexample. FIG. 9 is an entire configuration diagram showing refrigerantflow paths or the like in the defrosting operation of this embodiment,in which the flow of refrigerant in the heat pump cycle 10 is indicatedby a solid line and the flow of coolant in the coolant circulationcircuit 40 is indicated by a dashed arrow.

Specifically, a shutter device 65 is formed by combining a plurality ofcantilever door plates. The shutter device 65 is designed to open theinflow route for flowing the outside air into the radiator 43 bydisplacing the door plate in the direction parallel to the flow of airfrom the blower fan 17, and to close the inflow route for flowing theoutside air into the radiator 43 by displacing the door plate in thedirection intersecting the air flow from the blower fan 17.

The radiator 43 is positioned on the windward side in the flow directionX of the outside air blown by the blower fan 17 with respect to theoutdoor heat exchanger 16. The shutter device 65 closes the inflow routefor flowing the outside air into the radiator 43 to thereby block theinflow route for flowing the outside air into the outdoor heat exchanger16.

The shutter device 65 may be composed of a slide door or the like. Theshutter device 65 is driven by a servo motor (not shown) whose operationis controlled by a control signal output from the air conditioningcontroller.

In this embodiment, in the defrosting operation, the shutter device 65is operated to close the inflow route for flowing the outside air intothe radiator 43, and in other operation modes, the shutter device 65 isoperated to open the inflow route for flowing the outside air into theradiator 43. Thus, during the defrosting operation, the volume ofoutside air flowing into the heat-absorption air passage 16 b and intothe heat-dissipation air passage 43 b is decreased. The structures andoperations of other components in this embodiment are the same as thosein the first embodiment.

Thus, even the operation of the air conditioner 1 for the vehicle ofthis embodiment can provide the same effects as those of the firstembodiment. Further, in this embodiment, the shutter device 65 isoperated to close the inlet route for flowing the outside air into theradiator 43 during the defrosting operation, which can prevent theinflow of the outside air into the heat-absorption air passages 16 b andthe heat dissipation air passage 43 b due to the ram air pressure duringthe traveling of the vehicle.

Sixth Embodiment

In this embodiment, unlike the first embodiment, the specific structureof the heat exchanger structure 70 is modified, which will be describedbelow by way of example. The details of the heat exchanger structure 70will be explained below using FIGS. 10 to 13. FIG. 10 shows aperspective view of the contour of the heat exchanger structure 70 ofthis embodiment. FIG. 11 is an exploded perspective view of the heatexchanger structure 70. FIG. 12 is a cross-sectional view taken alongthe line A-A of FIG. 10. FIG. 13 is an exemplary perspective view forexplaining the flow of refrigerant and the flow of coolant in the heatexchanger structure 70.

First, as shown in the exploded perspective view of FIG. 11, in the heatexchanger structure 70 of this embodiment, the refrigerant tubes 16 a ofthe outdoor heat exchanger 16 are arranged in two lines and the coolingfluid tubes 43 a of the radiator 43 are also arranged in two lines, inthe flow direction X of the outside air blown by the blower fan 17.Further, the refrigerant tubes 16 a and the cooling fluid tubes 43 a arealternately arranged and laminated over each other.

Thus, in this embodiment, the heat-absorption air passage 16 b and theheat-dissipation air passage 43 b form one space. The outer fins 50which are the same as those of the first embodiment are arranged in theheat-absorption air passage 16 b and the heat-dissipation air passage 43b which form one space, and the respective outer fins 50 are bonded tothe tubes 16 a and 43 a.

On one end side (lower end side shown in FIGS. 10 to 13) in thelongitudinal direction of the refrigerant tubes 16 a and the coolingfluid tubes 43 a 43 a, a tank 16 c on the refrigerant side is providedfor collecting or distributing the refrigerant flowing through therefrigerant tubes 16 a. On the other end side (upper end side shown inFIGS. 10 to 13) in the longitudinal direction, a tank 43 c on thecooling fluid side is provided for collecting or distributing therefrigerant flowing through the tubes 43 a for cooling fluid.

The refrigerant side tank 16 c and the cooling fluid side tank 43 c havethe same basic structure. First, the refrigerant side tank 16 c includesa refrigerant side plate 161 for connection to the refrigerant tubes 16a and the cooling fluid tubes 43 a which are respectively arranged intwo lines, a refrigerant side intermediate plate 162 to be fixed to therefrigerant side connection plate 161, and a refrigerant side tank 163.

As shown in the cross-sectional view of FIG. 12, the refrigerant sideintermediate plate 162 is fixed to the refrigerant side connection plate161 to form a plurality of recesses 162 b for forming a plurality ofspaces in communication with the cooling fluid tubes 43 a, between therefrigerant side connection plate 161 and the plate 162 itself. Thesespaces serve as a communicating space for the cooling fluid thatconnects and communicates the cooling fluid tubes 43 a together arrangedin two lines in the flow direction X of the outside air.

FIG. 12 shows the cross section of the surroundings of recesses 432 bprovided in the cooling fluid side intermediate plate 432 for clearlyillustration. As mentioned above, since the refrigerant side tank 16 chas the same basic structure as that of the cooling fluid side tank 43c, the refrigerant side connection plate 161 and the recesses 162 b arerepresented in parentheses.

A through hole 162 a is provided at a part of the refrigerant sideintermediate plate 162 corresponding to the refrigerant tube 16 a topenetrate both sides of the plate. The refrigerant tube 16 a is insertedinto the through hole. Thus, on one end of the refrigerant side tank 16c, the refrigerant tube 16 a protrudes toward the refrigerant side tank16 c as compared to the cooling fluid tube 43 a.

The refrigerant side tank 163 is fixed to the refrigerant sideconnection plate 161 and the refrigerant side intermediate plate 162 toform a collection space 163 a for collecting therein the refrigerant anda distribution space 163 b for distributing the refrigerant.Specifically, the refrigerant side tank 163 is formed by pressing ametal plate in double mountain shape (W-like shape) as viewed in thelongitudinal direction.

The center of the double mountain shape of the refrigerant side tank 163is bonded to the refrigerant side intermediate plate 162 to participatethe tank 163 into the collection space 163 a and the distribution space163 b. In this embodiment, the collection space 163 a is disposed on thewindward side of the flow direction X of the outside air, and thedistribution space 163 b is disposed on the leeward side of the flowdirection X of the outside air.

One end of the refrigerant side tank 163 in the longitudinal directionis connected to a refrigerant inflow pipe 164 for flowing therefrigerant into the distribution space 163 b, and to a refrigerantoutflow pipe 165 for flowing the refrigerant from the collection space163 a. The other end of the refrigerant side tank 163 in thelongitudinal direction is closed by a closing member.

On the other hand, the cooling fluid side tank 43 c with the samestructure as described above also includes a cooling fluid sideconnection plate 431, a cooling fluid side intermediate plate 432 fixedto the plate 431, and a cooling fluid side tank 433.

As shown in the cross-sectional view shown in FIG. 12, a refrigerantcommunication space that can communicate the two-lined the refrigeranttubes 16 a together in the flow direction X of the outside air is formedby the recesses 432 b provided in the cooling fluid side intermediateplate 432 between the cooling fluid side connection plate 431 and thecooling fluid side intermediate plate 432.

A through hole 432 a is provided at a part of the cooling fluid sideintermediate plate 432 corresponding to the cooling fluid tube 43 a topenetrate both sides of the plate. The cooling fluid tube 43 a isinserted into the through hole. Thus, on the side of the cooling fluidside tank 43 c, the cooling fluid tube 43 a protrudes toward the coolingfluid side tank 43 c as compared to the refrigerant tube 16 a.

Further, the cooling fluid side tank 433 is fixed to the cooling fluidside connection plate 431 and the cooling fluid side intermediate plate432 to form a collection space 433 a for collecting therein the coolingmedia and a distribution space 433 b for distributing the cooling media.Specifically, in this embodiment, the distribution space 433 b isdisposed on the windward side of the flow direction X of the outsideair, and the collection space 433 a is disposed on the leeward side ofthe flow direction X of the outside air.

One end of the cooling fluid side tank 433 in the longitudinal directionis connected to a cooling fluid inflow pipe 434 for flowing the coolingfluid into the distribution space 433 b, and to a cooling fluid outflowpipe 435 for flowing the cooling fluid from the collection space 433 a.The other end of the cooling fluid side tank 43 c in the longitudinaldirection is closed by a closing member.

Thus, in the heat exchanger structure 70 of this embodiment, as shown inthe exemplary perspective view of FIG. 13, the refrigerant flowing intothe distribution space 163 b of the refrigerant side tank 16 c via therefrigerant inflow pipe 164 flows into each refrigerant tube 16 adisposed on the leeward side in the flow direction X of the outside airamong the refrigerant tubes 16 a arranged in two lines.

And, the refrigerant flowing from each refrigerant tube 16 a disposed onthe leeward side flows into each refrigerant tube 16 a disposed on thewindward side in the flow direction X of the outside air via a spaceformed between the cooling fluid side connection plate 431 of thecooling fluid side tank 43 c and the cooling fluid side intermediateplate 432.

Then, as indicated by a solid arrow in FIG. 13, the refrigerants flowingfrom the refrigerant tubes 16 a disposed on the windward side arecollected into the collection space 163 a of the refrigerant side tank16 c, and then flow from the refrigerant outlet pipe 165. That is, inthe heat exchanger structure 70 of this embodiment, the refrigerantflows turning around from the refrigerant tubes 16 a on the leeward sideto the cooling fluid side tank 43 c, and the refrigerant tubes 16 a onthe windward side in that order.

Likewise, as illustrated by the dashed arrow in FIG. 13, the coolantflows turning around from the cooling fluid tubes 43 a on the windwardside to the refrigerant side tank 16 c, and the cooling fluid tubes 43 aon the leeward side in that order. The structures and operations ofother components in this embodiment are the same as those in the firstembodiment. Even the operation of the air conditioning 1 for the vehicleof this embodiment can provide the same effects as those of the firstembodiment.

Further, in this embodiment, the refrigerant tubes 16 a and the coolingfluid tubes 43 a in the heat exchanger structure 70 are alternatelyarranged and laminated, so that the outdoor heat exchanger 16 can beeffectively defrosted during the defrosting operation.

That is, in the heat exchanger structure 70 of this embodiment, therefrigerant tube 16 a is disposed between the cooling fluid tubes 43 a,and the cooling fluid tube 43 a is disposed between the refrigeranttubes 16 a, whereby the heat-absorption air passage 16 b and theheat-dissipation air passage 43 b form one air passage.

As compared to the case where the radiator 43 and the outdoor heatexchanger 16 are disposed in series with respect to the flow direction Xof the outside air, in this embodiment, the tube 43 ab for the coolingfluid and the refrigerant tube 16 a can be arranged close to each other.Thus, the cooling fluid tube 43 a can be disposed near the frostgenerated in the refrigerant tube 16 a. As a result, the outdoor heatexchanger 16 can be effectively defrosted in the defrosting operation.The heat exchanger structure 70 of this embodiment may be applied to theheat pump cycles 10 of the second to fifth embodiments.

Seventh Embodiment

In the above first embodiment, the air conditioning controller stops theoperation of the compressor 11 during the defrosting operation, by wayof example. If the operation of the compressor 11 is stopped during thedefrosting operation, the indoor condenser 12 cannot heat the air. As aresult, the controller might blow the air having at a temperature lowerthan the temperature desired by the passenger in the vehicle. Once thedefrosting operation is started, the passenger can feel unsatisfied withheating.

In contrast, in this embodiment, even when the air cannot be heated bythe indoor condenser 12 in the defrosting operation, the vehicleinterior linkage control is performed for suppressing the loss inheating to the passenger. The linkage control will be described belowusing the flowcharts shown in FIGS. 14 to 17.

FIG. 14 is a flowchart showing a basic control flow of the vehicleinterior linkage control. The basic control flow is executed as asub-routine which is an interrupt process for a main routine to beexecuted by the air conditioner 1 for the vehicle. When a defrostingflag deffg indicative of the execution of the defrosting operation doesnot become 1 within a predetermined time assigned as an execution timeof the basic control flow, the operation returns to the main routine.

In step S100 of the basic control flow, a defrosting determinationprocess is executed to determine whether or not the frost is formed atthe outdoor heat exchanger 16 and whether or not the defrosting isperformed. The details of the defrosting determination process will bedescribed using FIG. 15. In step S101 of FIG. 15, the defrosting flagdeffg or the like is initialized.

Subsequently, in step S102, it is determined whether or not the frost isformed at the outdoor heat exchanger 16. Specifically, when thetemperature of the outer surface of the heat exchanger 16 is determinedto be equal to or less than 0° C., the frost is determined to be formed,and then, the operation proceeds to step S103 with the deffg kept to 1(deffg=1). In contrast, when the temperature of the outer surface of theoutdoor heat exchanger 16 is determined not to be equal to or less than0° C., the frost is determined not to be formed, and then, the operationreturns to step S102 again with the deffg kept to zero (deffg=0).

In step S103, it is determined whether the engine is operated or not.When the engine is determined to be operated in step S103, the deffg iskept to 1 (deffg=1), and the operation proceeds to step S104. When theengine is determined not to be operated, the operation proceeds to anair conditioning mode changing control shown in step S200 of FIG. 14.

In step S104, like step S102, it is determined whether the frost isformed at the outer heat exchanger 16 or not. Specifically, when thetemperature of the outer surface of the outdoor heat exchanger 16 isdetermined to be equal to or less than 0° C., the frost is determined tobe formed, and then the operation proceeds to step S105 with the deffgkept to 1 (deffg=1). When the temperature of the outer surface of theoutdoor heat exchanger 16 is determined not to be equal to or less than0° C., the frost is determined not to be formed, and then the operationreturns again to step S102.

In step S105, it is determined whether or not the coolant temperature Twreaches the predetermined defrosting reference temperature KTwdef. Instep S105, when the coolant temperature Tw is determined to reach thepredetermined defrosting reference temperature KTwdef (in thisembodiment, 10° C.), the outdoor heat exchanger 16 can be defrosted byflowing the coolant into the radiator 43, and then the operationproceeds to step S106 with the deffg kept to 1 (deffg=1).

In step S105, when the coolant temperature Tw is determined not to reachthe predetermined defrosting reference temperature KTwdef, even if thecoolant flows into the radiator 43, the outdoor heat exchanger 16 cannotbe defrosted, and then the operation returns to step S102 again.

In step S106, it is determined whether or not an inside air temperature(temperature of the vehicle interior) Tr detected by the inside airsensor is equal to or more than a predetermined reference inside airtemperature KTr (15° C. in this embodiment). In step S106, when theinside air temperature Tr is determined to be equal to or more than thereference inside air temperature KTr, the temperature of the vehicleinterior is hot enough for a general passenger not to feel unsatisfiedwith the cold (hereinafter referred to as a “warm-up state”), and thenthe operation proceeds to step S107 with the deffg kept to 1 (deffg=1).

In step S106, when the inside air temperature Tr is determined not to beequal to or more than the reference inside air temperature KTr, theinside air temperature Tr is not increased until the warm-up state. Inorder to give the heating of the vehicle interior a priority over thedefrosting operation, the operation returns again to step S102.

In step S107, it is determined whether or not the vehicle speed duringtraveling is equal to or less than a predetermined reference vehiclespeed (20 km/h in this embodiment). In step S107, when the vehicle speedis determined to be equal to or less than the predetermined referencevehicle speed, like the first embodiment, the defrosting can beeffectively performed together with the decrease in ram air pressure.Then, the operation proceeds to an air conditioning mode changingcontrol shown in step S200 of FIG. 14 with deffg kept to 1 (deffg=1).

As can be seen from the above description, a control step S100 of thisembodiment serves as a control portion with a frost formationdetermination portion for determining the frost formation of the outdoorheat exchanger 16. More specifically, the control steps S102 and S104serve as the frost formation determination portion.

Then, the air conditioning mode changing control to be performed in stepS200 will be described below using FIG. 16. The air conditioning modechanging control is to be exercised when the defrosting flag deffg isdetermined to be 1 by the defrosting determination process in step S100.

In step S201, first, a control signal to be output to the electric motorof the compressor 11 is determined such that the compressor 11 does notexhibit the refrigerant discharge capacity, that is, such that thecompressor 11 is stopped. In the following step S202, a control signalto be output to the blower 32 is determined such that the air blowingcapacity of the blower 32 is decreased by a predetermined capacity valuefrom the present capacity.

In the following step S203, a suction port mode is set to the inside airmode. That is, the ratio of introduction of inside air to outside air isincreased as compared to the state before the transmission to thedefrosting operation. In step S204, an air outlet mode is set to thefoot mode. That is, switching is performed to the air outlet mode forblowing the air mainly from the foot air outlet. Then, the operationproceeds to a defrosting start completion control shown in step S300 ofFIG. 14.

The defrosting start completion control executed in step S300 will bedescribed below using FIG. 17. In step S301, first, as described in thefirst embodiment, the three-way valve 42 of the coolant circulationcircuit 40 is switched such that the coolant flows into the radiator 43.Further, the coolant squeezing capacity of the coolant pump 41 ismaximized, the timer is actuated, and then the operation proceeds tostep S302.

In step S302, it is determined whether the vehicle speed duringtraveling is equal to or less than a predetermined reference vehiclespeed (in this embodiment, 20 km/h). When the vehicle speed isdetermined to be equal to or less than the reference vehicle speed instep S302, the effective defrosting can be achieved, and then theoperation proceeds to step S303. When the vehicle speed is determinednot to be equal to or less than the reference vehicle speed, theeffective defrosting cannot be performed, and then the operationproceeds to step S304.

In step S303, it is determined whether or not the elapsed time of thedefrosting operation exceeds a predetermined reference defrosting timeusing the timer actuated in step S301. When the elapsed time of thedefrosting operation is determined to exceed the reference defrostingtime, the operation proceeds to step S304. In step S304, at that time,the three-way valve 42 is switched such that the coolant flows into thebypass passage 44.

Then, the coolant squeezing capacity of the coolant pump 41 is changedto become the same squeezing capacity as that before the start of thedefrosting operation, and the timer is reset. Thereafter, the operationproceeds to an air conditioning mode returning control shown in stepS400 of FIG. 14. In the air conditioning mode returning control in stepS400, the blowing capacity of the blower 32, the suction port mode, andthe air outlet mode are returned to the same levels as those before thedefrosting operation. Then, the operation proceeds to step S500.

In step S500, it is determined whether stopping of the vehicle system isrequested or not. When the stopping of the vehicle system is notrequired, the operation proceeds to step S100. When the stopping of thevehicle system is required, the control processing is stopped. Thestructures and operations of other components of this embodiment are thesame as those of the first embodiment.

Thus, this embodiment can obtain the same effects as those of the firstembodiment. Additionally, in this embodiment, even when the airconditioning controller stops the operation of the compressor 11, andthe indoor condenser 12 cannot exhibit the heating capacity during thedefrosting operation, the above vehicle interior linkage control can beperformed to prevent the passenger from feeling unsatisfied withheating.

That is, in this embodiment, as described in the control step S106, thedefrosting operation is performed after the warm-up state is achieved,which can prevent the passenger from feeling unsatisfied with heating.As described in the control step S203, during the defrosting operation,the suction port mode is changed to the inside air mode. The inside airhaving a higher temperature than the outside air is circulated andblown, which can also prevent the passenger from feeling unsatisfiedwith heating.

As described in the control step S202, the blowing capacity of theblower 32 is decreased in the defrosting operation, which can preventthe passenger from feeling unsatisfied with heating even when thetemperature of air blown into the vehicle compartment is decreased. Atthis time, as described in the control step S204, the air outlet mode isset to the foot mode, which can effectively prevent the passenger fromfeeling unsatisfied with the heating as compared to the case where theair is blown toward the passenger's face.

As can be seen from the above description, this embodiment can beconsidered as the example of application of the heat pump cycle 10 tothe air conditioner) for a vehicle.

That is, this embodiment in one aspect includes a heat pump cycle whichhas a compressor for compressing and discharging refrigerant; auser-side heat exchanger (indoor condenser 12) for exchanging heatbetween the refrigerant discharged from the compressor and air blowninto a vehicle interior; a decompression device (fixed throttle 13 forheating) for decompressing the refrigerant flowing from the user-sideheat exchanger; an outdoor heat exchanger for allowing the refrigerantdecompressed by the decompression device to exchange heat with outsideair to evaporate itself; a heat-dissipation heat exchanger (radiator 43)disposed in a cooling fluid circulation circuit for circulating acooling fluid for cooling a vehicle-mounted device (electric motor MGfor traveling) generating heat in operation, and adapted to exchangeheat between the cooling fluid and outside air to dissipate heat fromthe cooling fluid; a cooling fluid circuit for flowing the cooling fluidinto the heat-dissipation heat exchanger (43); and cooling fluid circuitswitching device (42) for performing switching to another cooling fluidcircuit for allowing the cooling fluid to bypass the heat-dissipationheat exchanger (43). This embodiment also includes inside airtemperature detection portion for detecting an inside air temperature inthe vehicle interior; and a frost formation determination portion fordetermining frost formation at the outdoor heat exchanger. The outdoorheat exchanger includes a refrigerant tube for flowing the refrigerantdecompressed by the decompression device. A heat-absorption air passagefor flowing outside air is formed around the refrigerant tube. Theheat-dissipation heat exchanger includes a cooling fluid tube forflowing the cooling fluid. An heat-dissipation air passage for flowingoutside air is formed around the tubes for the cooling fluid. The airpassage for the heat absorption and the air passage for the heatdissipation are provided with an outer fin that enables the heattransfer between the refrigerant tube and the cooling fluid tube, whilepromoting the heat exchange in both heat exchangers. When the frost isdetermined to be formed at the outdoor heat exchanger by the frostformation determination portion, and an inside air temperature Tr of thevehicle interior is equal to or more than a predetermined referenceinside air temperature KTr, then the cooling fluid circuit switchingdevice can perform switching to the cooling fluid circuit for flowingthe cooling fluid to the heat dissipation heat exchanger.

This embodiment in another aspect includes the above heat pump cycle, afrost formation determination portion for determining the frostformation of the outdoor heat exchanger, and a casing for accommodatingtherein the user-side heat exchanger and for forming an air passage. Aninside/outside air switching device (inside/outside air switch 33) isdisposed in the casing to change the ratio of introduction of the insideair to the outside air to be introduced into the casing. When the frostis determined to be formed in the outdoor heat exchanger by the frostformation determination portion, the cooling fluid circuit switchingdevice performs switching to a cooling fluid circuit for flowing thecooling fluid to the heat dissipation heat exchanger. When the frost isdetermined to be formed in the outdoor heat exchanger by the frostformation determination portion, the inside/outside air switching devicecan increase the ratio of introduction of the inside air to the outsideair as compared to before transfer to the defrosting operation.

This embodiment in another aspect includes the above heat pump cycle, afrost formation determination portion for determining the frostformation of the outdoor heat exchanger, and a casing for accommodatingtherein the user-side heat exchanger and for forming an air passage. Anair outlet mode switching device is disposed in the casing to switchamong air outlet modes by changing opening/closing states of a pluralityof air outlets for blowing the air into the vehicle interior. As the airoutlet, a foot air outlet is provided for blowing the air toward atleast the foot of a passenger. When the frost is determined to be formedat the outdoor heat exchanger by the frost formation determinationportion, the cooling fluid circuit switching device performs switchingto a cooling fluid circuit for flowing the cooling fluid to the heatdissipation heat exchanger. When the frost is determined to be formed atthe outdoor heat exchanger by the frost formation determination portion,the air outlet mode switching device can perform switching to the airoutlet mode for blowing the air from the foot air outlet.

This embodiment in another aspect includes the above heat pump cycle, afrost formation determination portion for determining the frostformation at the outdoor heat exchanger, a casing for accommodating theuser-side heat exchanger therein and for forming an air passage, andblowing means (e.g., blower 32) disposed in the casing for blowing theair toward the vehicle interior. When the frost is determined to beformed at the outdoor heat exchanger by the frost formationdetermination portion, the cooling fluid circuit switching deviceperforms switching to a cooling fluid circuit for flowing the coolingfluid into the heat-dissipation heat exchanger. When the frost isdetermined to be formed at the outer heat exchanger by the frostformation determination portion, the blower means can decreases itsblowing capacity as compared to before the determination of the frostformation.

This embodiment in another aspect includes the above heat pump cycle,and a frost formation determination portion for determining the frostformation of the outdoor heat exchanger. When the vehicle speed of thetraveling vehicle is equal to or less than a predetermined referencevehicle speed, and the refrigerant temperature on the outlet side of theoutdoor heat exchanger is equal to or less than 0° C., the frost isdetermined to be formed at the outdoor heat exchanger. When the frost isdetermined to be formed at the outdoor heat exchanger by the frostformation determination portion, the cooling fluid circuit switchingdevice can perform switching to the cooling fluid circuit for flowingthe cooling fluid to the heat-dissipation heat exchanger.

Eighth Embodiment

Although in the above first and seventh embodiments, the operation ofthe compressor 11 is stopped during the defrosting operation by way ofexample, in this embodiment as shown in FIG. 18, the cycle structure ofthe heat pump cycle 10 is changed to achieve the heating of the vehicleinterior, while performing the defrosting operation like the thirdembodiment by way of example. FIG. 18 is an entire configuration diagramof the heat pump cycle 10 during the defrosting operation in thisembodiment, corresponding to FIG. 2 of the first embodiment.

Specifically, this embodiment differs from the first embodiment in thata variable throttle 83 for heating is employed which is capable ofchanging the opening degree of throttle as a decompression device forthe heating operation. The variable throttle 83 for heating includes avalve body whose throttle opening degree is variable, and an electricactuator comprised of a stepping motor for changing the throttle openingdegree of the valve body. The variable throttle 83 has its operationcontrolled by a control signal output from the air conditioningcontroller.

In this embodiment, the air conditioning controller controls the valveopening degree of the variable throttle 83 for heating to apredetermined opening degree in the heating operation and in the wasteheat collecting operation, and increases the valve opening degree of thevariable throttle 83 for heating in the defrosting operation, ascompared to the heating operation and the waste heat collectingoperation. Thus, in the defrosting operation, the high-pressurerefrigerant with a higher temperature discharged from the compressor 11is apt to flow into the outdoor heat exchanger 16 as compared to beforethe defrosting operation.

The structures and operations of other components of this embodiment arethe same as those of the first embodiment. Thus, in the air conditioner1 for the vehicle of this embodiment, the throttle opening degree of thevariable throttle 83 for heating is increased in the defrostingoperation, so that the high-pressure refrigerant at a high temperaturecan flow into the outdoor heat exchanger 16 to thereby promote thedefrosting of the outdoor heat exchanger 16. Further, during thedefrosting operation, the heating capacity of the indoor condenser 12for heating the air can be exhibited to perform heating of the vehicleinterior.

As viewed from the flow direction of the outside air, the positionalrelationship between a heat exchange region on a refrigerant inlet sideof the outdoor heat exchanger 16 and a heat exchange region on arefrigerant outlet side thereof does not change with respect to a heatexchanger region of the radiator 43, which can suppress the largefluctuations in amount of the heat transfer between the refrigerantflowing through the refrigerant tubes 16 a and the cooling fluid flowingthrough the cooling fluid tubes 43 a, like the third embodiment.

Ninth Embodiment

As shown in the entire configuration diagram of FIG. 19, in thisembodiment, the cycle structure of the heat pump cycle 10 is changed toachieve the heating of the vehicle interior, while performing thedefrosting operation like the eighth embodiment by way of example. FIG.19 is an entire configuration diagram of the heat pump cycle 10 in thedefrosting operation according to this embodiment, which corresponds toFIG. 2 of the first embodiment.

Specifically, this embodiment differs from the first embodiment in thatan outflow rate adjustment valve 84 is added for adjusting an outflowrate of the refrigerant flowing from the outdoor heat exchanger 16. Theoutflow rate adjustment valve 84 has the same basic structure as that ofthe variable throttle 83 for the heating of the eighth embodiment, andthus is integral with the refrigerant outlet of the outdoor heatexchanger 16.

In this embodiment, the air conditioning controller fully opens thevalve opening degree of the outflow rate adjustment valve 84 in theheating operation, the waste heat collection operation, and the coolingoperation, and reduces the valve opening degree of the outflow rateadjustment valve 84 in the defrosting operation as compared to in theheating operation, the waste heat collecting operation, and the coolingoperation. Thus, in the defrosting operation, an inflow rate of therefrigerant flowing into the outdoor heat exchanger 16 is decreased ascompared to before the transfer to the defrosting operation. Thestructures and operations of other components of this embodiment are thesame as those of the first embodiment.

In the air conditioner 1 for a vehicle of this embodiment, the valveopening degree of the outflow rate adjustment valve 84 is decreased inthe defrosting operation, so that the inflow rate of the refrigerantflowing into the outdoor heat exchanger 16 can be decreased, which canprovide the same effects as those of the eighth embodiment.

Since the outflow rate adjustment valve 84 is integrally structured witha refrigerant outlet of the outdoor heat exchanger 16, the volume of therefrigerant passage leading from the discharge port of the compressor 11to the inlet side of the outlet rate adjustment valve 84 can bedecreased to thereby quickly decrease the flow rate of the refrigerantflowing into the outdoor heat exchanger 16.

Tenth and Eleventh Embodiments

In the above third, eighth, and ninth embodiments, the outdoor heatexchanger 16 exhibits the heating capacity to achieve the heating of thevehicle interior without stopping the operation of the compressor 11 inthe defrosting operation, by way of example. In the ninth embodiment, asshown in FIG. 20, a PTC heater 85 is disposed in the casing 31 of theindoor air conditioning unit 30, and serves as a heating element forgenerating heat by being supplied with power.

The PTC heater 85 is disposed on the downstream side of the air flow ofthe indoor condenser 12, and generates heat by being supplied with powerfrom the air conditioning controller in the defrosting operation. Thus,even when the air conditioning controller stops the operation of thecompressor 11 during the defrosting operation, the PTC heater 85 canfunction as an auxiliary heater to heat the air, thereby achieving theheating of the vehicle interior.

In the eleventh embodiment, as shown in FIG. 21, a heater core 86 isprovided for exchanging heat between the engine coolant as a heat fluid,and the air. The heater core 86 has the same basic structure as that ofthe heater core 63 of the second embodiment. The heater core 86 isdisposed on the downstream side of the air flow of the indoor condenser12 to allow the engine coolant to flow thereinto during the defrostingoperation.

Thus, even when the air conditioning controller stops the operation ofthe compressor 11 during the defrosting operation, the heater core 86can function as an auxiliary heater to heat the air, thereby achievingthe heating of the vehicle interior. The heat fluid serving as a heatsource for heating the air at the heater core 86 is not limited to theengine coolant, but may be coolant or the like for cooling thevehicle-mounted devices generating heat in operation, such as theelectric motor MG for traveling, or an inverter.

Alternatively, both the PTC heater 85 of the tenth embodiment and theheater core 86 of the eleventh embodiment may be disposed on thedownstream side of the air flow of the indoor condenser 12 to serve asthe auxiliary heater. FIGS. 20 and 21 are the entire configurationdiagrams of the heat pump cycle 10 in the defrosting operation accordingto the ninth and eleventh embodiment, respectively, and correspond toFIG. 2 of the first embodiment.

Other Embodiments

The present invention is not limited to the above embodiments, andvarious modifications and changes can be made to the above embodimentswithout departing from the scope of the invention as follows.

(1) In the above embodiments, the vehicle-mounted device (external heatsource) generating heat in operation is the electric motor MG fortraveling, by way of example, but the external heat source is notlimited thereto. For example, when the heat pump cycle 10 is applied tothe air conditioner 1 for the vehicle, an engine or an electric device,such as an inverter, for supplying power to the electric motor MG fortraveling can be used as the external heat source.

In using the engine as the external heat source, the heat contained notonly in the engine coolant, but also in engine exhaust gas may be usedfor defrosting. Further, in applying the heat pump cycle 10 to astationary air conditioner, a cool storage, a cooling and heating devicefor a vending machine, and the like, the engine, the electric motor, andother electric devices which serve as the driving source for thecompressor of the heat pump cycle 10 can be used as the external heatsource.

(2) In the above embodiments, the electric three-way valve 42 isemployed as circuit switching device for switching among the coolingfluid circuits of the coolant circulation circuit 40, but the circuitswitching device is not limited thereto. For example, a thermostat valvemay be used. Thermostat valve is a cooling fluid temperature-responsivevalve comprised of a mechanical mechanism that opens and closes acooling fluid passage by displacing a valve body using a thermo wax(temperature sensing member) whose volume is changed by the temperature.Thus, the use of thermostat valve can also remove the coolanttemperature sensor 52.

(3) In the above embodiments, the refrigerant tubes 16 a of the outdoorheat exchanger 16, the cooling fluid tubes 43 a of the radiator 43, andthe outer fins 50 are formed of an aluminum alloy (metal) and bondedtogether by brazing. Obviously, the outer fins 50 may be formed of othermaterials with excellent heat conductivity (for example, a carbonnanotube or the like), and these elements may be bonded together withother bonding means, such as an adhesive.

(4) In the above embodiments, in the normal heating operation, switchingis performed to a cooling fluid circuit for allowing the coolant tobypass the radiator 43, which stores the heat dissipated from theelectric motor MG for traveling in the coolant. Alternatively oradditionally, a heat storage case (heat storing device) foraccommodating a heat storing material, such as paraffin, may be disposedin the coolant circulation circuit 40, whereby the heat dissipated fromthe electric motor MG for traveling may be stored in the heat storagecase in the normal heating operation.

Alternatively or additionally, a heating element (for example, PTCheater) that generates heat by being supplied with power may be disposedin the coolant circulation circuit 40, so that the heat dissipated fromthe heating element may be stored in the coolant in the normal heatingoperation. Alternatively, the heat dissipated from at least one of thevehicle-mounted device and the heating element that generates heat inthe operation of the electric motor MG for traveling and the like may bestored in the coolant. At this time, the amount of heat generated in theheating element is desirably controlled to increase with decreasingoutside air temperature so as to avoid the unnecessary powerconsumption.

(5) In the above first embodiment, when the vehicle speed is equal to orless than the predetermined reference vehicle speed (20 km/h in thisembodiment) and the refrigerant temperature Te on the outlet side of theoutdoor heat exchanger 16 is equal to or less than 0° C., the frostformation determination portion is used to determine whether the frostis formed at the outdoor heat exchanger 16, by way of example. However,the determination conditions for the frost formation are not limitedthereto.

For example, temperature detection portion for detecting the temperatureof the outer fin 50 of the outdoor heat exchanger 16 may be provided,and when the temperature detected by the temperature detection portionis equal to or less than the predetermined frost formation referencetemperature (for example, −5° C.), the frost may be determined to beformed.

(6) In the above embodiments, the means for stopping the operation ofthe blower fan 17 in the defrosting operation is used to decrease thevolume of outside air flowing into the heat-absorption air passage 16 band the heat-dissipation air passage 43 b, by way of example. Regardlessof the normal operation and the defrosting operation, when thecompressor 11 is stopped, the blowing capacity of the blower fan 17 maybe increased until a predetermined time has elapsed. Thus, when thecompressor 11 is stopped, the blowing capacity of the blower fan 17 canbe increased, so that the temperature of the outdoor heat exchanger 16can be quickly increased to the same level as the outside airtemperature.

(7) The structures described in the above respective embodiments may beapplied to other embodiments. For example, the vehicle indoor linkagecontrol described in the seventh embodiment may be executed in the airconditioner for a vehicle to which the heat pump cycle 10 of each of thesecond to fifth, and eighth to eleventh embodiments is applied.

For example, when the vehicle interior linkage control of the seventhembodiment is applied to the heat pump cycle 10 of the third embodiment,the air conditioning controller may open the opening/closing valve 15 cin the air conditioning mode changing control in the control step S200without stopping the operation of the compressor 11. When applied to thefourth embodiment, the opening/closing valve 15 a and theopening/closing valve 15 c may be opened by air conditioning modechanging control in the control step S200.

Likewise, when applied to the eighth embodiment, the valve openingdegree of the variable throttle 83 for heating may be reduced in the airconditioning mode changing control in the control step S200. Whenapplied to the ninth embodiment, the valve opening degree of the outflowrate adjustment valve 84 may be reduced in the air conditioning modechanging control in the control step S200.

(8) Although in the above embodiments, normal flon-based refrigerant isused as the refrigerant, by way of example, the refrigerant is notlimited thereto. Natural refrigerant, such as carbon dioxide, and acarbon-hydride refrigerant and the like may be used. Further, the heatpump cycle 10 may form a supercritical refrigeration cycle in which thepressure of refrigerant discharged from the compressor 11 is equal to orhigher than the critical pressure of the refrigerant.

1-26. (canceled)
 27. A heat pump cycle comprising: a compressorcompressing and discharging refrigerant; a user-side heat exchangerexchanging heat between the refrigerant discharged from the compressorand a heat exchange fluid; a decompression device decompressing therefrigerant flowing from the user-side heat exchanger; an outdoor heatexchanger which causes the refrigerant decompressed by the decompressiondevice to exchange heat with outside air and to be evaporated, the heatpump cycle being adapted to perform a defrosting operation fordefrosting the outdoor heat exchanger when the outdoor heat exchanger isfrosted; an indoor evaporator for allowing the refrigerant on adownstream side of the outdoor heat exchanger to exchange heat with theheat exchange fluid and to be evaporated; a refrigerant flow pathswitching device configured to switch a refrigerant flow path in aheating operation in which the refrigerant discharged from thecompressor flows into the user-side heat exchanger to heat the heatexchange fluid, and a refrigerant flow path in a cooling operation inwhich the refrigerant dissipating heat therefrom at the outdoor heatexchanger flows into the indoor evaporator to cool the heat exchangefluid, a heat-dissipation heat exchanger, disposed in a cooling fluidcirculation circuit for circulating a cooling fluid for cooling anexternal heat source, the heat-dissipation heat exchanger being adaptedto exchange heat between the cooling fluid and the outside air; and acooling fluid circuit switching device configured to switch between acooling fluid circuit for allowing the cooling fluid to flow into theheat-dissipation heat exchanger, and a cooling fluid circuit forallowing the cooling fluid to bypass the heat-dissipation heatexchanger, wherein the outdoor heat exchanger includes a refrigeranttube in which the refrigerant decompressed by the decompression deviceflows, a heat-absorption air passage for flowing the outside air isformed around the refrigerant tube, the heat-dissipation heat exchangerincludes a cooling fluid tube in which the cooling fluid flows, aheat-dissipation air passage for flowing the outside air is formedaround the cooling fluid tube, the heat-absorption air passage and theheat-dissipation air passage are provided with an outer fin that enablesheat transfer between the refrigerant tube and the cooling fluid tube,while promoting heat exchange in both of the outdoor heat exchanger andthe heat-dissipation heat exchanger, the cooling fluid circuit switchingdevice performs switching to the cooling fluid circuit for flowing thecooling fluid into the heat-dissipation heat exchanger in at least thedefrosting operation, a flow direction of the refrigerant flowingthrough the refrigerant tube in the heating operation is the same asthat of the refrigerant flowing through the refrigerant tube in thecooling operation, a heat exchange region at a refrigerant inlet side ofthe outdoor heat exchanger is overlapped in an outside air flowdirection with a heat exchange region at a cooling fluid inlet side ofthe heat dissipation heat exchanger, the outdoor heat exchanger isconfigured, such that relatively high-temperature refrigerant flowsthrough the heat exchange region at the refrigerant inlet side of theoutdoor heat exchanger in the cooling operation, and relativelylow-temperature refrigerant flows through the heat exchange region atthe refrigerant inlet side of the outdoor heat exchanger in the heatingoperation, and the heat dissipation heat exchanger is configured, suchthat relatively high-temperature cooling fluid flows through the heatexchange region at the refrigerant inlet side of the heat dissipationheat exchanger in both the cooling operation and the heating operation.28. The heat pump cycle according to claim 27, wherein in the defrostingoperation, an inflow rate of the refrigerant flowing into the outdoorheat exchanger is decreased as compared to before transfer to thedefrosting operation.
 29. The heat pump cycle according to claim 27,wherein the decompression device is a variable throttle mechanism inwhich a throttle opening degree is variable, and the decompressiondevice increases the throttle opening degree in the defrosting operationas compared to before transfer to the defrosting operation.
 30. The heatpump cycle according to claim 27, further comprising an outflow rateadjustment valve configured to adjust an outflow rate of the refrigerantflowing from the outdoor heat exchanger, wherein the outflow rateadjustment valve decreases the outflow rate of the refrigerant in thedefrosting operation as compared to before transfer to the defrostingoperation.
 31. The heat pump cycle according to claim 30, wherein theoutflow rate adjustment valve is configured integrally with an outletfor the refrigerant of the outdoor heat exchanger.
 32. The heat pumpcycle according to claim 27, further comprising an outdoor blower whichblows the outside air toward both the outdoor heat exchanger and theheat-dissipation heat exchanger, wherein the outdoor blower increases anair blowing capacity when the compressor is stopped, as compared tobefore stopping the compressor.
 33. The heat pump cycle according toclaim 27, wherein in the defrosting operation, a heating capacity of theuser-side heat exchanger for heating the heat exchange fluid isdecreased as compared to before transfer to the defrosting operation.34. The heat pump cycle according to claim 27, wherein theheat-absorption air passage and the heat-dissipation air passage areconfigured such that volumes of the outside air flowing into theheat-absorption air passage and the heat-dissipation air passage aredecreased in the defrosting operation.
 35. The heat pump cycle accordingto claim 27, further comprising an outdoor blower which blows theoutside air toward both the outdoor heat exchanger and theheat-dissipation heat exchanger, wherein the heat-dissipation heatexchanger is located on a windward side in the flow direction of theoutside air blown by the outdoor blower with respect to the outdoor heatexchanger.
 36. The heat pump cycle according to claim 27, wherein atleast one of the refrigerant tubes is located between the cooling fluidtubes, at least one of the cooling fluid tubes is located between therefrigerant tubes, and at least one of the heat-absorption air passageand the heat-dissipation air passage is formed as one air passage. 37.The heat pump cycle according to claim 27 being applied to an airconditioner for a vehicle, the heat pump cycle further comprising: aninside air temperature detection portion configured to detect an insideair temperature of a vehicle interior; and a frost formationdetermination portion configured to determine frost formation of theoutdoor heat exchanger, wherein the heat exchange fluid is air blowninto the vehicle interior, the external heat source is a vehicle-mounteddevice generating heat in operation, the cooling fluid is a coolant forcooling the vehicle-mounted device, and the cooling fluid circuitswitching device performs switching to the cooling fluid circuit forflowing the cooling fluid into the heat-dissipation heat exchanger whenthe frost is determined to be formed at the outdoor heat exchanger bythe frost formation determination portion and an inside air temperatureof the vehicle interior is equal to or more than a predeterminedreference inside air temperature.
 38. The heat pump cycle according toclaim 27 being applied to an air conditioner for a vehicle, the heatpump cycle further comprising a frost formation determination portionfor determining frost formation of the outdoor heat exchanger, whereinthe heat exchange fluid is air blown into the vehicle interior, theexternal heat source is a vehicle-mounted device generating heat inoperation, the cooling fluid is a coolant for cooling thevehicle-mounted device, the user-side heat exchanger is disposed in acasing forming therein an air passage, an inside/outside air switchingdevice for changing a ratio of introduction of inside air to outside airto be introduced into the casing is disposed in the casing, wherein thecooling fluid circuit switching device performs switching to the coolingfluid circuit for flowing the cooling fluid to the heat-dissipation heatexchanger when the frost is determined to be formed at the outdoor heatexchanger by the frost formation determination portion, and theinside/outside air switching device increases the ratio of introductionof the inside air to the outside air as compared to before transfer tothe defrosting operation when the frost is determined to be formed atthe outdoor heat exchanger by the frost formation determination portion.39. The heat pump cycle according to claim 27 being applied to an airconditioner for a vehicle, the heat pump cycle further comprising afrost formation determination portion configured to determine frostformation of the outdoor heat exchanger, wherein the heat exchange fluidis air blown into the vehicle interior, the external heat source is avehicle-mounted device generating heat in operation, the cooling fluidis a coolant for cooling the vehicle-mounted device, the user-side heatexchanger is disposed in a casing forming therein an air passage, an airoutlet mode switching device for switching among air outlet modes bychanging opening/closing states of air outlets for blowing the air intothe vehicle interior is disposed in the casing, at least a foot airoutlet for blowing the air to a foot of a passenger is provided as theair outlet, the cooling fluid circuit switching device performsswitching to the cooling fluid circuit for flowing the cooling fluidinto the heat-dissipation heat exchanger when the frost is determined tobe formed at the outdoor heat exchanger by the frost formationdetermination portion, and the air outlet mode switching device performsswitching to the air outlet mode for blowing the air from the foot airoutlet when the frost is determined to be formed at the outdoor heatexchanger by the frost formation determination portion.
 40. The heatpump cycle according to claim 27 being applied to an air conditioner fora vehicle, the heat pump cycle further comprising a frost formationdetermination portion configured to determine frost formation of theoutdoor heat exchanger, wherein the heat exchange fluid is air blowninto the vehicle interior, the external heat source is a vehicle-mounteddevice generating heat in operation, the cooling fluid is a coolant forcooling the vehicle-mounted device, the user-side heat exchanger isdisposed in a casing for forming therein an air passage, a blower forblowing air toward the vehicle interior is disposed in the casing, thecooling fluid circuit switching device performs switching to the coolingfluid circuit for flowing the cooling fluid into the heat-dissipationheat exchanger when the frost is determined to be formed at the outdoorheat exchanger by the frost formation determination portion, and theblower decreases an air blowing capacity, as compared to before thedetermination of the frost formation.
 41. The heat pump cycle accordingto claim 27 being applied to an air conditioner for a vehicle, the heatpump cycle further comprising a frost formation determination portionfor determining frost formation of the outdoor heat exchanger, whereinthe heat exchange fluid is air blown into the vehicle interior, theexternal heat source is a vehicle-mounted device generating heat inoperation, the cooling fluid is a coolant for cooling thevehicle-mounted device, the frost formation determination portiondetermines that the frost is formed at the outdoor heat exchanger, whena vehicle speed is equal to or less than a predetermined referencespeed, and when a temperature of the refrigerant on an outlet side ofthe outdoor heat exchanger is equal to or less than 0□□C, and thecooling fluid circuit switching device performs switching to a coolingfluid circuit for flowing the cooling fluid into the heat-dissipationheat exchanger when the frost is determined to be formed at the outdoorheat exchanger by the frost formation determination portion.
 42. Theheat pump cycle according to claim 41, wherein the frost formationdetermination portion determines that the frost is formed at the outdoorheat exchanger, when the speed of the traveling vehicle is equal to orless than the predetermined reference speed, and when the temperature ofthe refrigerant on the outlet side of the outdoor heat exchanger isequal to or less than 0□□C.
 43. The heat pump cycle according to claim37, further comprising a coolant temperature detection portionconfigured to detect a temperature of the coolant flowing into avehicle-mounted device, wherein the cooling fluid circuit switchingdevice performs switching to the cooling fluid circuit for flowing thecooling fluid into the heat-dissipation heat exchanger when a coolanttemperature detected by the coolant temperature detection portion isequal to or more than the predetermined reference temperature.
 44. Theheat pump cycle according to claim 27, wherein the cooling fluidcirculation circuit stores therein the heat contained in the externalheat source when the cooling fluid circuit switching device performsswitching to the cooling fluid circuit for allowing the cooling fluid tobypass the heat-dissipation heat exchanger.
 45. The heat pump cycleaccording to claim 44 being applied to an air conditioner for a vehicle,wherein the heat exchange fluid is air blown into the vehicle interior,the external heat source is a vehicle-mounted device generating heat inoperation, the cooling fluid is a coolant for cooling thevehicle-mounted device, and the cooling fluid circulation circuit storesheat dissipated from the vehicle-mounted device in the coolant when thecooling fluid circuit switching device performs switching to the coolingfluid circuit for allowing the cooling fluid to bypass theheat-dissipation heat exchanger.
 46. The heat pump cycle according toclaim 44 being applied to an air conditioner for a vehicle, wherein theheat exchange fluid is air blown into the vehicle interior, the externalheat source is a heating element for generating heat by being suppliedwith power, the cooling fluid is a coolant for cooling the heatingelement, and the cooling fluid circulation circuit stores the heatdissipated from the heating element in the coolant when the coolingfluid circuit switching device performs switching to the cooling fluidcircuit for allowing the cooling fluid to bypass the heat-dissipationheat exchanger.
 47. The heat pump cycle according to claim 44 beingapplied to an air conditioner for a vehicle, wherein the heat exchangefluid is air blown into the vehicle interior, a vehicle-mounted devicegenerating heat in operation, and a heating element for generating heatby being supplied with power are provided as the external heat source,the cooling fluid is a coolant for cooling the heating element and thevehicle-mounted device, and the cooling fluid circulation circuit storesthe heat dissipated from at least one of the vehicle-mounted device andthe heating element in the coolant when the cooling fluid circuitswitching device performs switching to the cooling fluid circuit forallowing the cooling fluid to bypass the heat-dissipation heatexchanger.
 48. The heat pump cycle according to claim 46, wherein theheating element has an amount of generated heat therefrom controlledbased on an outside air temperature.
 49. The heat pump cycle accordingto claim 27, further comprising: an outdoor unit bypass passage whichcauses the refrigerant decompressed by the decompression device tobypass the outdoor heat exchanger and to guide the refrigerant to arefrigerant outlet side of the outdoor heat exchanger; and anoutdoor-unit bypass passage switching device configured to switchbetween a refrigerant circuit for guiding the refrigerant decompressedby the decompression device to the outdoor heat exchanger, and arefrigerant circuit for guiding the refrigerant decompressed by thedecompression device toward the outdoor unit bypass passage, wherein inthe defrosting operation, the outdoor unit bypass passage switchingdevice performs switching to the refrigerant circuit for guiding therefrigerant decompressed by the decompression device to the outdoor unitbypass passage.
 50. The heat pump cycle according to claim 27, furthercomprising: an indoor evaporator which exchanges heat between therefrigerant on a downstream side of the outdoor heat exchanger and theheat exchange fluid; an evaporator bypass passage which causes therefrigerant on the downstream side of the outdoor heat exchanger tobypass the indoor evaporator and to guide the refrigerant to arefrigerant outlet of the indoor evaporator; and an evaporator bypasspassage switching device configured to switch a refrigerant circuit forguiding the refrigerant on the downstream side of the outdoor heatexchanger to the indoor evaporator, and a refrigerant circuit forguiding the refrigerant on the downstream side of the outdoor heatexchanger to the evaporator bypass passage, wherein in the defrostingoperation, the evaporator bypass passage switching device performsswitching to the refrigerant circuit for guiding the refrigerant on thedownstream side of the outdoor heat exchanger to the indoor evaporator.51. The heat pump cycle according to claim 27 being applied to an airconditioner for a vehicle, wherein the heat exchange fluid is air blowninto the vehicle interior, the user-side heat exchanger is disposed in acasing for forming therein an air blowing passage, and in the casing, anauxiliary heater is provided for heating the air blown into the vehicleinterior using as a heating source, at least one of a heating fluidheated by a vehicle-mounted device that generates heat in operation, anda heating element that generates heat by being supplied with power.